Migration from ADFS to PHS

We have a EDU tenant of 15K users. A month ago we have migrated from ADFS to PHS (using staged roll-out). We still have a limted number of applications using adfs.

We notice a lot of issues with byod mac users after the migration. Flushing their cookies in Safari didn't seem to help, using another browser most of the time did help.

Also the number of "Invalid username or password" errors has doubled since the migration on the 2nd of March. While the weeks before every user was already on PHS through staged roll-out. The number of users initiating SSPR has also increased 5-fold.

Is this expected? Is there an explanation for the difficult transition for byod mac users?