Also, I think that Command+, (that’s a comma) will bring up application settings.
Here is part of the tablet event record when I draw a short diagonal line on my tablet:
Stylus move X=188.29 Y=318.09 B=1 P=50.9% S=0.1 (DRAW)
Stylus move X=186.61 Y=320.03 B=1 P=52.2% S=0.2 (DRAW)
Stylus move X=184.93 Y=322.30 B=1 P=54.5% S=0.2 (DRAW)
Stylus move X=183.07 Y=324.56 B=1 P=56.6% S=0.3 (DRAW)
Stylus move X=181.22 Y=326.61 B=1 P=57.8% S=0.3 (DRAW)
Stylus move X=179.54 Y=328.44 B=1 P=59.5% S=0.3 (DRAW)
Stylus move X=177.68 Y=329.95 B=1 P=60.5% S=0.3 (DRAW)
Stylus move X=176.00 Y=331.46 B=1 P=60.9% S=0.3 (DRAW)
Stylus move X=174.48 Y=332.54 B=1 P=61.4% S=0.3 (DRAW)
Stylus move X=173.14 Y=333.51 B=1 P=61.5% S=0.3 (DRAW)
It’s recognised as a ‘Stylus’.
There are smoothly continuously changing X/Y coordinate signals being received.
You have very low pressure signals. Maybe you applied low pressure at the time.
Which brush preset were you using?
In your case, krita is receiving oscillating X/Y coordinate values from the
tablet → driver → OS pathway.
I’ve no idea why it could be doing that but krita can only work with what it is given.
You could try reading these topics to see if anything helps:
Search results for 'H420' - Krita Artists
Maybe this one?:
Huion H420 Tablet not working