Incoming Mails in update incident page changes state from assigned to pending

[AkshayRaut]

On update Incident page I have functionality to send and receive mail and I have added assignee to it. On sending any mail the state of ticket remains unchanged, but on incoming mail, the state of ticket gets changed to pending. I want to avoid this state change and this needs to done at the module level only and not at the postmaster filter level as the requirement is at module level only and from postmaster filter level it works fine. I made changes in all the files and added new filter to keep state unchanged, still on incoming mails the state gets changed to pending. Please provide me some knowledge insights and solutions like what am I missing any configuration