Bitbucket Server connecting from Azure DevOps - error 128/403

[John Smith]

Scenario :

In Azure DevOps we are using a Bitbucket user account that has been setup with a PAT (actually has multiple PATs for different tasks) to do various git commands etc - now this works the majority of the time, then intermittently fails saying:

fatal: unable to access 'https://user:pw@mybitbucketserver.com/git/scm/myproject/blah.git/ : The requested URL returned error: 403
##[warning]Git fetch failed with exit code 128, back off 3.922 seconds before retry.
##[command]git fetch --force --tags --prune --progress --no-recurse-submodules origin
fatal: unable to access 'https://user:pw@mybitbucketserver.com/git/scm/myproject/blah.git/ : The requested URL returned error: 403
##[warning]Git fetch failed with exit code 128, back off 1.634 seconds before retry.
##[command]git fetch --force --tags --prune --progress --no-recurse-submodules origin
fatal: unable to access 'https://user:pw@mybitbucketserver.com/git/scm/myproject/blah.git/ : The requested URL returned error: 403
##[error]Git fetch failed with exit code:128
##[section]Finishing: Checkout

Is there any sort of limit that needs to be configured to allow more connections/openfiles/etc etc ? to allow for a lot of requests ?

Any help much appreciated.