If I understand correctly the whole system worked properly before decorating?
As far as I know a flashing stdby light usually indicates that the BV tries to `communicate`with external devices, but it`s not working properly.
I would disconnect ALL masterlink devices - BV7 (40 - MK II?), BV10, BV1, BS5... for 5 - 10 minutes. Maybe it`s better to disconnect also the freesat box, HDR 1 and PS3. Especially HDR1 is also connected via scart that includes datalink...
Reconnect them one after the other with BV7 as videomaster being the last one. Don`t start up the system immediately, wait 30 - 60 seconds.
This helped in some cases with my (earlier) 7-40 MKII, when I changed the setup.
Good luck and welcome to Beoworld.
Stefan