Hi shannon-rivas,
I could replicate you mentioned behavior.
I prepared 2 calendars. One is "Standard" calendar and other is "Standard_test" calendar and it has a lot of Non-Workday.
I defined Developer Role who uses "Standard_test" calendar and Resource1 who uses "Standard" calendar.
I added Developer Role as Team staff. Allocation of Developer is very small because it uses"Standard_test" calendar.
Next step, I replaced this Developer Role to Resource1.
The Allocation of Resource1 was different from Developer. It became to large amount of hours.
It sounds like what John posted above.
Regards,
Shoichi