Have Y plan,boiler glowworm hxi condensing,room stat honeywell T6060B, program randall 4033. Just replaced 3 port valve.Working ok, on both water and CH and both together. However unable to stop heating by room stat or switching programmer off, have to stop with isolating switch. tried other stat still the same.When switched back on have to turn up stat to start heating as normal. Wiring problem ?