Refresh and synchronisation problem with Gmail IMAP on Mcbook

Hi, I have a Mcbook Pro running High Sierra 10.13.6. Have several email (Gmail) accounts set up on my MacBook. Has been working well till two days ago. Suddenly mails from one of my mail ID's has stopped downloading to my mac book except when I quit mail and relaunch. When I relaunch, all mails received since this problem began downloads again even though I had deleted them on my macbook.

The activity window shows a 'Moving Message' stuck at a particular count & continuous activity in download messages.

I have this email ID set up on my android phone and iPad. It works fine on these devices. Other accounts are set up only on mac book and work fine.

I dont want to rebuild this mail account as I dont want to lose the old messages that are all sorted in various local mailboxes,. Can any one help please? Thanx