Hi @Future, welcome to the forum 
There were some changes in 4.1.1 to the attitude control (to try to fix some previous issues with the roll and pitch control drifting), although I would recommend updating to the latest stable firmware to make sure you didn’t install one of the 4.1.1 beta releases partway through the attitude control changes.
You could also try installing the current 4.5 beta release, in case it includes a fix for your issue as a result of changes from one of the other vehicle firmwares.
If those firmwares don’t help, then please provide an autopilot log (preferably a DataFlash (.bin) log from the flight controller, but a telemetry log (.tlog) recorded by your control station software or MAVLink router would still be useful), and if possible a more detailed description of what you’re expecting to happen vs what you’re observing, so we can try to replicate and fix the issue.
It’s also worth making sure you haven’t accidentally activated input hold mode via a joystick button, although that shouldn’t persist across autopilot/vehicle restarts, so is unlikely the cause of your issue if the problem is repeatable.
This may be an issue of gimbal lock - in general 90° rotations can cause motion axes to line up in a way that certain angle representations can’t differentiate between two axes, and accordingly reduces the autopilot’s ability to interpret attitude commands around those points, as well as to represent its current state in angles that are easy to interpret. There’s some additional information in this comment.
EDIT: I’ve just found your duplicate post, and merged it in here. Creating multiple posts of the same topic makes it more likely we’ll also duplicate our efforts in responding, and means we have less time for giving meaningful responses to other posts and questions.
Please only make one post for a given topic. If your question doesn’t get fully answered or your problem remains unresolved you can bump the post to the top of the feed by commenting follow-ups with additional information / things you’ve tried that haven’t worked, or if it’s related to a product problem you can make a support request and include a link to your original forum post to provide context.