Three tasks with high frequency with 2 counters methods, 50103 error

I will try to be simple:

We have one chassis 9189 with 8 modules, two of them are used to take frequency mesurements (9401), let's say module 6 and module 7.

I need mesuring frequency on three encoders, so I configured module 6 ctr 0/1 for frequency 1, module 6 ctr 2/3 for frequency 2, as i'm using 2 counters methods, in that case it works fine.

The problem is that when i added the third mesurement on module 7 ctr 0/1, i got 50103 error as the system considered the ctr 0/1 are reserved even it is on module 6.

What i should do in such configuration?

Thanks a lots