It's the RCBS beam scale.
I'm assuming the 505 since the 1010 has been discontinued. (Those were Cadillacs, btw). I like beam scales, it's impossible to forget to zero them. As long as you have a flat level surface and you don't move it after you zero you should be good. But it's still important to check them against a standard periodically.
Something else to consider is if your neck tension adjustment on your seater die got changed, for instance when you switched bullets. Then maybe you switched back without changing the adjustment.
Is it possible you grabbed some magnum primers by accident?
I don't want to sound insulting, I'm just trying to jog your brain. I once loaded some .308 and when I got to the range, I had a FTF. When I extracted the case, the bullet was barely stuck in the lands. So I checked my rounds, and I had loaded a whole row without powder. This was irritating, because I always am very thorough and careful. And I shine a light in every case before seating to check for irregularities - such as missing powder. But I had finished these loads about 1:00 AM, and probably skipped that step by accident. Now I don't load when I'm tired. Shouldn't have before, but I had never made a mistake before either.