On my old PC there was software for transferring, but I will have access to it only in 2-3 days.
Try using browser plugins or Windows software. There are manuals on this issue on Github.
You need to try different versions of importers. Perhaps a conflict due to different versions, I had it. After migration, monitor the work site 24/7 host-tracker.com/InstantCheck/Create/?type=Http What versions of importers have you used?
You are not afraid that this will adversely affect attendance?