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That sounds - if by too high or too low, you mean displaced along the page in the direction of the shorter side of the average 8 1/2 by 11 inch page - as if the paper were not being fed consistently, or perhaps the punch is slightly out of alignment.
If the holes sometimes come out just right, but not by any means frequently, then it is most likely that either the paper feeding is erratic, or the hole punching parts are loose and joggle around a bit.
To keep the paper feeding rightly and consistently, slipping of the paper in the paper feed rollers' grasp should be prevented, by a cleaning of paper feed rollers in the machine, especially toward the end of the paper path. This should be done with the power Off, and with attention to not getting alcohol vapor on the fuser, and especially not on the 'drum' and/or 'imager' which are very sensitive indeed to moisture and vapors.
(And the fuser rollers should *not* be cleaned, they are not feed rollers and are unlikely to be responsible for the problem. And the drum should never be cleaned in any fashion, nor touched.)
Here's a procedure for cleaning the paper feed rollers:
If the problem might possibly be owing to aging roller surfaces (for paper is fed into faxes and printers with rubber or plastic cylindrical rollers, that propel the sheet into or through the machine)... then you might need to clean the rollers in the problem area where feeding is not going right.
Remove all paper from the machine, unplug it, and open it so as to have access to the rollers in the problem area where feeding is not being done properly.
Take a clean high-quality lint-free rag cloth, moisten it with rubbing alcohol, and rub the rollers firmly all over their paper-contacting surfaces, three times over.
(If the rollers are hard to reach, there is another way to clean them... let me know if that is the case, and I will detail how to do the cleaning.)
Allow 5+ minutes for drying-off, then reload the paper, close up the machine where you opened it up, and then try again.