When I drag a line with brush/pencil the tip travels up or down creating an uneven line. Cannot stop

In Photoshop CC 21, 24.2 my brush/pencil/mouse during free hand are stuck and will only make the same uneven line regardless of the tip I select..  If I try to free hand circles free hand the result is not a circle. Resetting all tool presets to default did not help. Uninstall/reinstall PS did not correct the problem.  I can only draw a straight line by holding shift down point to point.  I’m an intermediate user with a Intuos Pro M Tablet. On a number of occasions, the brush or pencil start out working normally for a short period but always changed. I cannot determine if something I’m doing triggers it. Mourse or pen