I had a silmilar situation a few years ago where the pdk had been updated. Something changed with the default values of the standard via definitions in the new pdk. This could be similar.
When you translate to OA, the vias themselves are not converted. They simply reference the via definitions in the new lib.
I think you may be converting symbolic or cdsvias to standard vias in OA.
With the -mapviaparams switch you are using the via default values from the instance masters of CDB instead of the default values from the standard vias in the OA pdk.
It is possible that things like layerenclosures are calculated differently in OA when defaults are used.
Check if you have values such as "NONE" in your original CDB techlib.
Or, simply try running the translator without the -mapviaparams switch
As always, if this doesn't help, contact customer support.