temperamental central locking

First time post. 1998 1.3 auto GX. The central locking has developed a mind of its own. Sometimes will lock up as soon as I shut the door - without inserting key in lock. Other times very reluctant to unlock, especially driver's door, and I have to turn key as if to lock and unlock a couple of times before it actually unlocks. Its actually my partner's car and she is now getting very nervous of driving it in case she finds herself stranded either locked in or locked out.

Any ideas of cause? Control unit on way out? Easier to bypass/disconnect than fix? If so what is best way to disable the unit? All suggestions welcome. Thanks