IP blocked for no apparent reason

I'm getting instances where I'm blocked from accessing my company's omnibus GitLab instance.
I'm the administrator, and it seems to be for no apparent reason.
It also seems to be on an exponential backoff schedule too. That is, the block seems to increase to the point where I couldn't access our site for an entire day.

Now one of our users has experienced the same issue.

Is there any way I can mitigate this, perhaps through an IP whitelist?