Is the message after which the crash occurs is still the same (Too long string during import)?
Could you please test it and, if repeatable, report this issue?
I have tried testing just now with importing backup to 8.4 2018.12.09 build 015 with strings longer than 20 symbols in phone number field and it worked fine - the system just "cut off" the exceeding amount of symbols.
If you are able to repeat this issue, please report it.
Kind regards,
HansaWorld Team