BFT controlled gates open but don't close

[John24hr]

Hi all - we've a couple of swing arm gates controlled by a BFT Aries.  The system is about 20 years old but has been reliable till now.

Recently the gates opened then wouldn't shut.  We could unlock the arms and manually shut them ok.  Once locked again they would open on demand perfectly but, once open fully, wouldn't close again.  There is plenty of ticking going on from the relays as the shut cycle is supposed to happen and there is even power to the motors (haven't tested polarity) - but no movement.  The gates move freely once unlocked

Any ideas much appreciated.