RCBS 505 issues

Seems my scales aren't holding zero value.
I set them to zero, gently move the slides to set correct weight. Weigh a charge of 44g, I then move everything back to zero the balance beam and notice the scales need adjusting. I adjust the scales and re weigh the 44g charge(tipped out of case) and the charge weight is incorrect.
Any idea on how to fix this if it is at all possible. I must have done something to my scales, I'm pretty careful with my equipment but something has happened. I only decided to check my scales as the last rounds I made were shooting all over the show. Thankfully I only made 30.

There isn't too much to go wrong with them, I would think changing zero must be something to do with the pivot point/surface. It might be as simple as a bit of grit or dust.

Mine are the older Ohaus 5-0-5 scales which I have had for about 50 years. Mine became a bit wonky that cleaning did not fix. It was a whisker from steel wool stuck on the magnet, almost invisible. A quick clean and they were back to normal.
GPM.

Cheers, will have a good look tonight and give them a clean. Mine are made by Ohaus but branded RCBS 505.

I have a set of Redding scales that were becoming a little less reliable. The following gave me excellent results.
Using a small artists paint brush, remove all dust.
Clean the V and brush on some graphite.
Sharpened the knife edge (very carefully with a small and extremely fine oil stone.
Replaced the magnets with stronger ones. This will not effect the accuracy but will reduce the time it takes to settle.
https://en.m.wikipedia.org/wiki/Magnetic_damping

After zeroing I have 2 check weights. About 40 and 100 grains. I use these to ensure the scale continue to be consistant.

Cigars got it - had the same issue with mine. Some dust on the pivot points.