If you could share with us screencaps/video of the following we can look into it as currently we are unable to replicate the issue on our side.
- List of plugins in your Plugin Manager
- Video/GIF of the Error as it is happening
- Console Log roughly when the Error happens
Because you mentioned that your project uses custom plugins, you can also send a share link to our business email for a GDrive/Dropbox/Mega folder that contains your project. This would allow us to offer more than a general solution to the issue and allow for a faster response. Once the problem is resolved, you may revoke our access to the project and we'll delete any files we have locally. If that doesn't work for you, that's totally fine, we can continue to go back and forth in this thread.