Outlook , multiple 365 a/c & emails stuck in outbox

Hi .Outlook 365(2019)multiple 365 domain email a/c's in the one Outlook profileIm have issues with emails getting stuck in the Outbox. I had MS support look at this last year it happening again.Ive tried reloading Office. Ive removed the Outlook profile & re-added the 365 email a/c'sFrom searching , Ive seen a few others with the same issue but no fix.Deleting stuck emails will clear them, but soon new emails will get stuck. Its not happening in the main/1st email a/c added in Outllook, its on the other a/c's I had read that having multiple exchange a/c's in a single Outlook profile can cause issues . There are 5 email a/c's in this profile , Im starting to think thats whats causing the issue

Any idea's, has anyone come across this before or found a long term fix ?