diff --git a/src/dmr/packet/ControlSignaling.cpp b/src/dmr/packet/ControlSignaling.cpp
index dede269d..968b3b36 100644
--- a/src/dmr/packet/ControlSignaling.cpp
+++ b/src/dmr/packet/ControlSignaling.cpp
@@ -867,6 +867,22 @@ bool ControlSignaling::writeRF_CSBK_Grant(uint32_t srcId, uint32_t dstId, uint8_
             }
         }
         else {
+            // do collision check between grants to see if a SU is attempting a "grant retry" or if this is a
+            // different source from the original grant
+            uint32_t grantedSrcId = m_tscc->m_affiliations->getGrantedSrcId(dstId);
+            if (srcId != grantedSrcId) {
+                if (!net) {
+                    LogWarning(LOG_RF, "DMR Slot %u, DT_CSBK, CSBKO_RAND (Random Access), SVC_KIND_VOICE_CALL (Voice Call) denied, traffic in progress, dstId = %u", m_tscc->m_slotNo, dstId);
+                    writeRF_CSBK_ACK_RSP(srcId, TS_DENY_RSN_TGT_BUSY, (grp) ? 1U : 0U);
+
+                    ::ActivityLog("DMR", true, "Slot %u group grant request %u to TG %u denied", m_tscc->m_slotNo, srcId, dstId);
+                    m_slot->m_rfState = RS_RF_REJECTED;
+                }
+
+                return false;
+            }
+
+
             chNo = m_tscc->m_affiliations->getGrantedCh(dstId);
             slot = m_tscc->m_affiliations->getGrantedSlot(dstId);
 
diff --git a/src/lookups/AffiliationLookup.h b/src/lookups/AffiliationLookup.h
index 08ac858d..15967de1 100644
--- a/src/lookups/AffiliationLookup.h
+++ b/src/lookups/AffiliationLookup.h
@@ -150,7 +150,7 @@ namespace lookups
         /// <summary>Helper to get the channel granted for the given destination ID.</summary>
         virtual uint32_t getGrantedCh(uint32_t dstId);
         /// <summary>Helper to get the source ID granted for the given destination ID.</summary>
-        virtual uint32_t getGrantedSrcId(uint32_t srcId);
+        virtual uint32_t getGrantedSrcId(uint32_t dstId);
 
         /// <summary>Helper to set RF channel data.</summary>
         void setRFChData(const std::unordered_map<uint32_t, VoiceChData>& chData) { m_rfChDataTable = chData; }
diff --git a/src/nxdn/packet/Trunk.cpp b/src/nxdn/packet/Trunk.cpp
index e3cc1e76..71793be9 100644
--- a/src/nxdn/packet/Trunk.cpp
+++ b/src/nxdn/packet/Trunk.cpp
@@ -536,7 +536,23 @@ bool Trunk::writeRF_Message_Grant(uint32_t srcId, uint32_t dstId, uint8_t servic
             }
         }
         else {
+            // do collision check between grants to see if a SU is attempting a "grant retry" or if this is a
+            // different source from the original grant
+            uint32_t grantedSrcId = m_nxdn->m_affiliations.getGrantedSrcId(dstId);
+            if (srcId != grantedSrcId) {
+                if (!net) {
+                    LogWarning(LOG_RF, "NXDN, " NXDN_RTCH_MSG_TYPE_VCALL_REQ " denied, traffic in progress, dstId = %u", dstId);
+                    writeRF_Message_Deny(0U, srcId, NXDN_CAUSE_VD_QUE_GRP_BUSY, RTCH_MESSAGE_TYPE_VCALL);
+
+                    ::ActivityLog("NXDN", true, "group grant request from %u to TG %u denied", srcId, dstId);
+                    m_nxdn->m_rfState = RS_RF_REJECTED;
+                }
+
+                return false;
+            }
+
             chNo = m_nxdn->m_affiliations.getGrantedCh(dstId);
+            m_nxdn->m_affiliations.touchGrant(dstId);
         }
     }
 
diff --git a/src/p25/packet/Trunk.cpp b/src/p25/packet/Trunk.cpp
index 4f541229..e1bf6f35 100644
--- a/src/p25/packet/Trunk.cpp
+++ b/src/p25/packet/Trunk.cpp
@@ -688,6 +688,9 @@ bool Trunk::processNetwork(uint8_t* data, uint32_t len, lc::LC& control, data::L
                             }
                         }
                         break;
+                        case TSBK_OSP_DVM_GIT_HASH:
+                            // ignore
+                            return true; // don't allow this to write to the air
                         default:
                             LogError(LOG_NET, P25_TSDU_STR ", unhandled LCO, mfId = $%02X, lco = $%02X", tsbk->getMFId(), tsbk->getLCO());
                             return false;
@@ -2224,6 +2227,21 @@ bool Trunk::writeRF_TSDU_Grant(uint32_t srcId, uint32_t dstId, uint8_t serviceOp
             }
         }
         else {
+            // do collision check between grants to see if a SU is attempting a "grant retry" or if this is a
+            // different source from the original grant
+            uint32_t grantedSrcId = m_p25->m_affiliations.getGrantedSrcId(dstId);
+            if (srcId != grantedSrcId) {
+                if (!net) {
+                    LogWarning(LOG_RF, P25_TSDU_STR ", TSBK_IOSP_GRP_VCH (Group Voice Channel Request) denied, traffic in progress, dstId = %u", dstId);
+                    writeRF_TSDU_Deny(srcId, dstId, P25_DENY_RSN_PTT_COLLIDE, (grp) ? TSBK_IOSP_GRP_VCH : TSBK_IOSP_UU_VCH);
+
+                    ::ActivityLog("P25", true, "group grant request from %u to TG %u denied", srcId, dstId);
+                    m_p25->m_rfState = RS_RF_REJECTED;
+                }
+
+                return false;
+            }
+
             chNo = m_p25->m_affiliations.getGrantedCh(dstId);
             m_p25->m_affiliations.touchGrant(dstId);
         }