Cut tool not working properly

I have been using Audacity for years with Windows to transform my records into files. I own since few days a brand new iMac, but I found a problem I can’t solve.
When I try to cut the usual few seconds of silence/scratches between the songs (or more between A side and B side), the tool ALWAYS cut the double or triple of the time, adding complete silence that arrives to ruin the end of the previous song and the beginning of the following song.
I did it successfully thousands of time on my old pc, without any problem, and now I tried every kind of possibility on the menu without result.
Thanks if someone helps.

Make sure Snap-To is not selected at the bottom of the Audacity work window.