I have been experiencing crashes mass editing for the past few months on FM21 and originally thought it was to do with the Mass Edit options as that is how I was mostly editing youngsters so I recently changed to create various presets in the preset manager, then search for players and then apply the preset.
On the latest test save I was running this seemed to fix the issue as I would make some changes then wait a few months and if the game didn't crash within that time then it seemed to be good. However after the latest edits the game is now crashing.
https://file.io/E0CrMd3PMrnv - Save file (too large for your upload)
I thought there was an issue with attributes going over the min and max limits (1 and 20) but when I look at the players I have recently edited I can't find any that have that issue. The changes I made were to hidden, mental and physical attributes along with CA, PA and rep changes. I also changed age on those that were 16 and 17 years old to -1 years.
I was concerned that editing age down to 14 can also cause issues so I now never bring down anyones age to below 15 but again this doesn't seem to be the problem here.
Aside from those changes I haven't made any other recently in the save aside from making a free agent physio have 20 Physiotherapy and then signing him to my team in Brazil. For this I created staff members using the in game editor, and then exporting the profile within FMRTE to upgrade staff (making sure their CA/PA is correct rather than guessing as you have to if just using FMRTE).
If you need any more information then let me know as it would be great to get this sorted. Thanks.