Grabbing an opacity slider while moving the mouse very quickly triggers tag dragging.

[MewPurPur]

This is easiest to reproduce with complex SVGs that cause a lot of lag.

[MewPurPur]

#505 made this issue quite a bit better, now the value only changes once :D

Still not a desired behavior, but it's less awful than before.

[MewPurPur]

This can be reproduced with other things too, just opacity sliders tend to cause the most lag so they are easiest to reproduce this with.