Strange Azure Service bus behaviour - subscription #2 is receiving message while subscription #1 is not - azure

Question

I am having some very strange issues with Azure Service Bus topic subscriptions. For the reference I have extracted the service bus topic configurations via service bus explorer and hoping somebody could point me into the right direction here. Really appreciate any help I can get.
Setup
I have 1 topic named topic2 and two subscription for this topic topicsub2 and topicsub3.
Issues
When publishing message to topic. Subscription topicsub3 recieves all messages that are sent while topicsub2 does not receive any messages. This behaviour is random, sometimes I would see messages in topicsub2 and sometimes the message is never delivered to the topicsub2 both subscriptions are using the same filters.
Followings are the few test scenarios that I have tried to figure out why this is happening.
I tried removing the filter from topicsub2 and sending message. But this had no impact still no messages. My assumption is that if no filters are applied all message for the topic will be forwarded to the subscription.
After removing the filter, I added default SQL filter (1=1) filter back to the subscription and tried sending message again it didn't work. I tried sending 5 messages to the topic, none of them appeared in the subscription topicsub2 and all were received by topicsub3.
I restarted the console application receiver (console application that reads from topicsub2) and tried sending messages again. This time it worked.
After about 10 mins, the subscription topicsub2 stopped receiving messages again.
Summary
This is where I am at. My investigation leads me this behaviour is random and there is some idling going on in topicsub2 that I am unaware of. Topicsub3 is working fine.
Can somebody please lead me into the right direction?
Following is the settings for topic 2 including the two subscriptions.
<?xml version="1.0" encoding="UTF-8"?>
<Entities xmlns="http://schemas.microsoft.com/servicebusexplorer" serviceBusNamespace="defaultstd">
<Topics>
<Topic>
<DefaultMessageTimeToLive>14.00:00:00</DefaultMessageTimeToLive>
<AutoDeleteOnIdle>10675199.02:48:05.4775807</AutoDeleteOnIdle>
<MaxSizeInMegabytes>1024</MaxSizeInMegabytes>
<RequiresDuplicateDetection>False</RequiresDuplicateDetection>
<DuplicateDetectionHistoryTimeWindow>00:10:00</DuplicateDetectionHistoryTimeWindow>
<Path>topic2</Path>
<EnableBatchedOperations>True</EnableBatchedOperations>
<SupportOrdering>False</SupportOrdering>
<EnableFilteringMessagesBeforePublishing>True</EnableFilteringMessagesBeforePublishing>
<IsAnonymousAccessible>False</IsAnonymousAccessible>
<Status>Active</Status>
<UserMetadata />
<EnablePartitioning>True</EnablePartitioning>
<EnableExpress>False</EnableExpress>
<IsReadOnly>False</IsReadOnly>
<Subscriptions>
<Subscription>
<LockDuration>00:00:30</LockDuration>
<RequiresSession>False</RequiresSession>
<DefaultMessageTimeToLive>14.00:00:00</DefaultMessageTimeToLive>
<AutoDeleteOnIdle>10675199.02:48:05.4775807</AutoDeleteOnIdle>
<EnableDeadLetteringOnMessageExpiration>True</EnableDeadLetteringOnMessageExpiration>
<EnableDeadLetteringOnFilterEvaluationExceptions>True</EnableDeadLetteringOnFilterEvaluationExceptions>
<TopicPath>topic2</TopicPath>
<Name>topicsub2</Name>
<MaxDeliveryCount>2</MaxDeliveryCount>
<EnableBatchedOperations>False</EnableBatchedOperations>
<Status>Active</Status>
<ForwardTo />
<ForwardDeadLetteredMessagesTo />
<UserMetadata />
<IsReadOnly>False</IsReadOnly>
<Rules>
<Rule>
<Filter>
<SqlFilter>
<SqlExpression>sys.Label NOT IN ('TestEvent')</SqlExpression>
<CompatibilityLevel>20</CompatibilityLevel>
</SqlFilter>
</Filter>
<Action>
<EmptyRuleAction />
</Action>
<Name>$Default</Name>
<IsReadOnly>True</IsReadOnly>
</Rule>
</Rules>
</Subscription>
<Subscription>
<LockDuration>00:00:30</LockDuration>
<RequiresSession>False</RequiresSession>
<DefaultMessageTimeToLive>14.00:00:00</DefaultMessageTimeToLive>
<AutoDeleteOnIdle>10675199.02:48:05.4775807</AutoDeleteOnIdle>
<EnableDeadLetteringOnMessageExpiration>True</EnableDeadLetteringOnMessageExpiration>
<EnableDeadLetteringOnFilterEvaluationExceptions>True</EnableDeadLetteringOnFilterEvaluationExceptions>
<TopicPath>topic2</TopicPath>
<Name>topicsub3</Name>
<MaxDeliveryCount>2</MaxDeliveryCount>
<EnableBatchedOperations>False</EnableBatchedOperations>
<Status>Active</Status>
<ForwardTo />
<ForwardDeadLetteredMessagesTo />
<UserMetadata />
<IsReadOnly>False</IsReadOnly>
<Rules>
<Rule>
<Filter>
<SqlFilter>
<SqlExpression>sys.Label NOT IN ('TestEvent')</SqlExpression>
<CompatibilityLevel>20</CompatibilityLevel>
</SqlFilter>
</Filter>
<Action>
<EmptyRuleAction />
</Action>
<Name>$Default</Name>
<IsReadOnly>True</IsReadOnly>
</Rule>
</Rules>
</Subscription>
</Subscriptions>
</Topic>
</Topics>
</Entities>