Dropout of amplicon 64

Anyone seeing dropout of amplicon 64? Have you been able to fix it?
TIA

We’ve tried dropping the PCR temperature a little (approx 2.5 degrees) and have seen recovery of that amplicon without any other negative effects.

As mentioned above, the amplicon 64 drops out at high temperature above 65 C.
Probably your thermal cycler generates bit higher temperature than the set value.