diff --git a/server/trackdirect/TrackDirectDataCollector.py b/server/trackdirect/TrackDirectDataCollector.py
index fa5d01f1bc943e24430c48bcb0fde09371e1d164..63959b197bf4dfc6724add2bfb144516423d34be 100644
--- a/server/trackdirect/TrackDirectDataCollector.py
+++ b/server/trackdirect/TrackDirectDataCollector.py
@@ -1,9 +1,6 @@
 import logging
-from twisted.python import log
 import psycopg2
 import psycopg2.extras
-from collections import deque
-import json
 import re
 import aprslib
 import datetime
@@ -17,7 +14,6 @@ from trackdirect.collector.PacketBatchInserter import PacketBatchInserter
 from trackdirect.exceptions.TrackDirectParseError import TrackDirectParseError
 from trackdirect.database.DatabaseConnection import DatabaseConnection
 from trackdirect.repositories.StationRepository import StationRepository
-from trackdirect.objects.Packet import Packet
 
 #from pympler.tracker import SummaryTracker
 
@@ -261,9 +257,10 @@ class TrackDirectDataCollector():
                 if (turnRate > 0) :
                     frequencyLimitToApply = int(frequencyLimitToApply / (1+turnRate))
 
-            if ((packet.timestamp - frequencyLimitToApply) < packet.markerPrevPacketTimestamp):
-                # This station is sending faster than config limit
-                return True
+            if packet.markerPrevPacketTimestamp:
+                if ((packet.timestamp - frequencyLimitToApply) < packet.markerPrevPacketTimestamp):
+                    # This station is sending faster than config limit
+                    return True
 
             if (packet.stationId in self.movingStationIdsWithVisiblePacket):
                 # This station is sending way to fast (we havn't even added the previous packet to database yet)
diff --git a/server/trackdirect/parser/policies/PacketRelatedMapSectorsPolicy.py b/server/trackdirect/parser/policies/PacketRelatedMapSectorsPolicy.py
index a083000fc40fdfb5f7567ebad900036150e6b977..08767d9f8d83af94a87f351ad8eafabd29e9a3b5 100644
--- a/server/trackdirect/parser/policies/PacketRelatedMapSectorsPolicy.py
+++ b/server/trackdirect/parser/policies/PacketRelatedMapSectorsPolicy.py
@@ -1,5 +1,3 @@
-import json
-import datetime
 import time
 
 from trackdirect.parser.policies.MapSectorPolicy import MapSectorPolicy
@@ -65,7 +63,7 @@ class PacketRelatedMapSectorsPolicy():
             # We only add related map-sectors to moving stations (that has a marker)
             if (packet.mapId == 1):
                 # If new packet is not confirmed (mapId 7) we connect it with related map-sectors later
-                if (previousPacket.markerCounter > 1
+                if (previousPacket.markerCounter is not None and previousPacket.markerCounter > 1
                         or packet.markerId == previousPacket.markerId):
                     # We only add related map-sectors if previous packet has a marker with several connected packet
                     # A packet with a marker that is not shared with anyone will be converted to a ghost-marker in client
diff --git a/server/trackdirect/repositories/PacketRepository.py b/server/trackdirect/repositories/PacketRepository.py
index 946fe4e762cdba0d35b58415f56103e83fa220b7..e9bca1a178389c7f41c3cdd5e55a403bbb8fa450 100644
--- a/server/trackdirect/repositories/PacketRepository.py
+++ b/server/trackdirect/repositories/PacketRepository.py
@@ -1,7 +1,3 @@
-import datetime
-import time
-import calendar
-import collections
 
 from trackdirect.common.Repository import Repository
 from trackdirect.objects.Packet import Packet
@@ -407,7 +403,7 @@ class PacketRepository(Repository):
         record = selectCursor.fetchone()
         selectCursor.close()
 
-        if (record is not None and record["latest_confirmed_packet_timestamp"] >= minTimestamp):
+        if (record is not None and record["latest_confirmed_packet_timestamp"] is not None and record["latest_confirmed_packet_timestamp"] >= minTimestamp):
             return self.getObjectByIdAndTimestamp(record["latest_confirmed_packet_id"], record["latest_confirmed_packet_timestamp"])
         else:
             return self.create()
@@ -431,7 +427,7 @@ class PacketRepository(Repository):
         record = selectCursor.fetchone()
         selectCursor.close()
 
-        if (record is not None and record["latest_location_packet_timestamp"] >= minTimestamp):
+        if (record is not None and record["latest_location_packet_timestamp"] is not None and record["latest_location_packet_timestamp"] >= minTimestamp):
             return self.getObjectByIdAndTimestamp(record["latest_location_packet_id"], record["latest_location_packet_timestamp"])
         else:
             return self.create()