First these aren't old school, in fact they were way ahead of their time - the first modern thin film emulsions
Treat with care but normally, keep all parts of the process cycle to a tightish temperature control +/- 1°C. I've used EFKE/Adox films since the early 1970's in all formats and in recent yerars they at least have some hardening, I've not had a problem in the past 20 years or so.
I haven't used a hardening fixer since the 1970's for any films and as long as you are careful these EFKE films shouldn't be a problem, use Photoflow as normal bt don't squeegee .
Usually issues with these emulsions are down to poor temerature control.