diff --git a/pallets/slow-clap/Cargo.toml b/pallets/slow-clap/Cargo.toml
index 49c68f1..a499bcb 100644
--- a/pallets/slow-clap/Cargo.toml
+++ b/pallets/slow-clap/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "ghost-slow-clap"
-version = "0.3.42"
+version = "0.3.43"
 description = "Applause protocol for the EVM bridge"
 license.workspace = true
 authors.workspace = true
diff --git a/pallets/slow-clap/src/lib.rs b/pallets/slow-clap/src/lib.rs
index f5b9f16..3e932ca 100644
--- a/pallets/slow-clap/src/lib.rs
+++ b/pallets/slow-clap/src/lib.rs
@@ -72,7 +72,7 @@ const LOG_TARGET: &str = "runtime::ghost-slow-clap";
 const DB_PREFIX: &[u8] = b"slow_clap::";
 
 const FETCH_TIMEOUT_PERIOD: u64 = 3_000;
-const LOCK_BLOCK_EXPIRATION: u64 = 10;
+const LOCK_BLOCK_EXPIRATION: u64 = 20;
 
 pub type AuthIndex = u32;
 
@@ -378,7 +378,8 @@ pub mod pallet {
 
         fn validate_unsigned(_source: TransactionSource, call: &Self::Call) -> TransactionValidity {
             if let Call::slow_clap { clap, signature } = call {
-                let authorities = Authorities::<T>::get(&clap.session_index);
+                let (session_index, _) = Self::mended_session_index(&clap);
+                let authorities = Authorities::<T>::get(&session_index);
                 let authority = match authorities.get(clap.authority_index as usize) {
                     Some(authority) => authority,
                     None => return InvalidTransaction::BadSigner.into(),
@@ -459,27 +460,49 @@ impl<T: Config> Pallet<T> {
         hex_str
     }
 
-    fn try_slow_clap(clap: &Clap<T::AccountId, NetworkIdOf<T>, BalanceOf<T>>) -> DispatchResult {
-        let authorities = Authorities::<T>::get(&clap.session_index);
-        ensure!(
-            authorities.get(clap.authority_index as usize).is_some(),
-            Error::<T>::NotAnAuthority
+    fn mended_session_index(
+        clap: &Clap<T::AccountId, NetworkIdOf<T>, BalanceOf<T>>,
+    ) -> (SessionIndex, H256) {
+        let prev_session_index = clap.session_index.saturating_sub(1);
+        let clap_unique_hash =
+            Self::generate_unique_hash(&clap.receiver, &clap.amount, &clap.network_id);
+
+        let received_claps_key = (
+            prev_session_index,
+            &clap.transaction_hash,
+            &clap_unique_hash,
         );
+
+        let session_index = ReceivedClaps::<T>::get(&received_claps_key)
+            .is_empty()
+            .then(|| clap.session_index)
+            .unwrap_or(prev_session_index);
+
+        (session_index, clap_unique_hash)
+    }
+
+    fn try_slow_clap(clap: &Clap<T::AccountId, NetworkIdOf<T>, BalanceOf<T>>) -> DispatchResult {
+        let (session_index, clap_unique_hash) = Self::mended_session_index(&clap);
+        let mut claps_in_session = ClapsInSession::<T>::get(&session_index);
+
         ensure!(
-            ClapsInSession::<T>::get(&clap.session_index)
+            claps_in_session
                 .get(&clap.authority_index)
                 .map(|info| !info.disabled)
                 .unwrap_or(true),
             Error::<T>::CurrentValidatorIsDisabled
         );
 
-        let clap_unique_hash =
-            Self::generate_unique_hash(&clap.receiver, &clap.amount, &clap.network_id);
-        let received_claps_key = (
-            clap.session_index,
-            &clap.transaction_hash,
-            &clap_unique_hash,
-        );
+        let disabled_authorites = claps_in_session
+            .values()
+            .filter(|info| info.disabled)
+            .count();
+
+        let active_authorities = Authorities::<T>::get(&session_index)
+            .len()
+            .saturating_sub(disabled_authorites);
+
+        let received_claps_key = (session_index, &clap.transaction_hash, &clap_unique_hash);
 
         let number_of_received_claps =
             ReceivedClaps::<T>::try_mutate(&received_claps_key, |tree_of_claps| {
@@ -498,15 +521,15 @@ impl<T: Config> Pallet<T> {
                 }
             })?;
 
-        ClapsInSession::<T>::mutate(&clap.session_index, |claps_details| {
-            (*claps_details)
-                .entry(clap.authority_index)
-                .and_modify(|individual| (*individual).claps.saturating_inc())
-                .or_insert(SessionAuthorityInfo {
-                    claps: 1u32,
-                    disabled: false,
-                });
-        });
+        claps_in_session
+            .entry(clap.authority_index)
+            .and_modify(|individual| individual.claps.saturating_inc())
+            .or_insert(SessionAuthorityInfo {
+                claps: 1u32,
+                disabled: false,
+            });
+
+        ClapsInSession::<T>::insert(&session_index, claps_in_session);
 
         Self::deposit_event(Event::<T>::Clapped {
             authority_id: clap.authority_index,
@@ -517,7 +540,7 @@ impl<T: Config> Pallet<T> {
         });
 
         let enough_authorities =
-            Perbill::from_rational(number_of_received_claps as u32, authorities.len() as u32)
+            Perbill::from_rational(number_of_received_claps as u32, active_authorities as u32)
                 > Perbill::from_percent(T::ApplauseThreshold::get());
 
         if enough_authorities {
@@ -1113,8 +1136,8 @@ impl<T: Config> OneSessionHandler<T::AccountId> for Pallet<T> {
     }
 
     fn on_before_session_ending() {
-        let session_index = T::ValidatorSet::session_index();
         let validators = T::ValidatorSet::validators();
+        let session_index = T::ValidatorSet::session_index().saturating_sub(1);
         let authorities_len = Authorities::<T>::get(&session_index).len();
         let claps_in_session = ClapsInSession::<T>::get(&session_index);