A 2 fs timestep is not recommended for CPT dynamics.
Do not use such a large ECHECK value, it only masks model building problems you should deal with.
The use of the legacy ISVFRQ feature is no longer recommended.
Possibly harmless, but ICHECW should be zero with a thermostat; however, you should consider heating from e.g. 198 K.
ORDER 6 is recommended with PME.
TMASS is in different units than PMASS, and is typically 5-10 times larger than PMASS.