If "A-Opt" at the BM4500 is really set to "1" the BM should not react on any video commands like "V.Tape"
Please disconnect the MCL wires to the Linkroom and the 2nd 1611 to the other Linkroom - only the TV and the
BM4500 are then connected via the 1611 Converter - as I mentioned before - during testing always KISS
(Keep It Straightforward and Simple)
Please set BM to A.Opt 1 again , set the BV 7-32 to "V-Opt" "1" and check the response of both units -
LED "twinkling" on the BV and "1" on display of BM 4500.
Then unplug the power of both units and the 1611 for a minimum of 1 min - connect to power again and wait
1 min before sending any commands by your remote - check if BM is still responding to "V.Tape"
If it does not respond you can proceed with the suggestions of my previous posting,
If the BM 4500 is still responding to video-commands (they should be ignored unless AV has been pressed before)
then your BM4500 is faulty and needs to be serviced