[BUG] Drawing masks does not work properly at high ROI counts?

[JannikMen]

Description
In certain areas of an image drawing a mask leads to one of three outcomes:
Case 1) Mask is drawn as a closed shape but appears as an open shape afterwards (single stroke is enabled)
Case 2) Mask cannot be drawn
Case 3) "Drawing mode" cannot be left. Cellpose has to be restarted.

Reproducing the issue
So far the issue only occured with in a single image and can be reproduced by trying to draw masks around certain areas. For other areas of the same image it works fine.

Log entries
Case 1) GUI_INFO: 1070 ROIs saved to C:/Users/janni/AppData/Local/CellposeEnvironment/P7-Tag2-40er-links_green_seg.npy
No extraordinary output in the console

Case 2) ERROR: cell too small without overlaps, not drawn
Eventhough drawing even smaller masks in other areas of the image works just fine

Case 3) QGraphicsScene::removeItem: item 0x139b23ac170's scene (0x0) is different from this scene (0x139b52600e0)
Appears for every pixel touched by the cursor

Screenshots

Here you can see an example of Case 1

Maybe the problem lies with the high number of ROIs? Previously edited images all had a lower ROI count