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this happened too often to being ignored.
When I am using eraser with the other side of the stylus, after erases I try to draw, but the tip is not pencil any more, but continues to erase. When I try to reach anything on panels, I discover program simply doesn't react. Only thing reacts is top menu, so I am at least able to save my work. After I save I quit the app, but, unfortunately, at this point it crashes. I already sent to Elodie the bug report with crash report Mac created, but I am writing this in order to maybe someone has a similar or the same problem.

I am using Intuous 4, MacOs X 10.5.8 and project is 4k full

I couldn't replicate the problem, but I'm on windows anyway.
What version of the Intuos driver are you using?

This is very weird; I wanted to emulate the issue and just discovered that my eraser end behaves exactly like the nib end. It even reacts to Sven's SWAP plugin so with the press of a key I can toggle between eraser and pen. I too have Intuos 4 but am on a PC -- I don't think Sven's plugin works on a Mac but that is what you need because it lets you give your nib any size of eraser you wish while you toggle between pen mode and eraser mode with the press of a key.

With eraser end you can pick what ever tool you like and than you can switch from tool to tool just by turning a stylus. I picked an eraser, sometimes I just need to erase part of image completely, not pressure sensitive like using the button on stylus. It works, but crashes sometimes, annoyingly. What I noticed is that this happens when line smoothing is turned on, and I already experienced system slowing down when drawing too fast with smoothing on, especially on high resolutions, like 4k. So, problem is maybe with processor or lack of memory.

So you are on a Mac; which version of TVPaint?

what is your configuration (processor, RAM, ...) ?