Switching receivers doesn't correct the problem. Sounds to me like the one 6131 is faulty.
Try this with it;
1. Check the software version, found under System Information. It must be at V170. If not, make sure it is connected to satellite and turn it off for 30 minutes to allow an update.
2. At home, disconnect it from the power, disconnect sat cable. Wait 1 minute
3. plug 6131 back into power, turn 6131 back on, wait for it to reboot LEAVE SATELLITE CABLE DISCONNECTED
4. Go into signal strength meter (Menu, 6, 1, 1), go to Check Switch and select Test. LET THE RECEIVER GO THROUGH ALL 38 TESTS, THIS MAY TAKE 15 MINUTES. DO NOT CANCEL.
5. Test should fail, indicated by all X's
6. At conclusion of test, if it still indicates SW44 with 91 and 82 as OK, that receiver is faulty and requires replacement.
7. If test did fail, indicated by all X's, then take it back to RV and run a Check Switch again using the RV dish and SW21.
Also, very important, be sure your home SW44 has the 91 satellite connected to 1A and 1B, and 82 satellite connected to 2A and 2B.
At RV, 91 connected to Dish 1, 82 connected to Dish on the SW21.
Very important due to switching voltages, correct Pinza???