Are you lobbing the putt at all, or doing more of a line drive? If you're too lobby then the high/low misses can be challenging...in too close and it's easy to be high, too far away and easy to be low. If you drive them a bit more then you have a long flight range that the disc is still at the correct height.
That being said if I tried to learn to putt with my left hand I'm sure I would be way more prone to one-off mistakes at random for a long time.
Also videoing your putt could be helpful, at minimum for you to see what it actually looks like.