On a machine that age they are microswitches; it is possible you have a switch hanging up. It is years since I had the covers off on my HL1 but I think the switche(s) you need to look at are inside and you have to remove the top plate behind the turret. Once you have the cover off you should be able to operate the switch by hand. On the diagnostics page somewhere I think you will find an entry for turret lock/unlock which should change between 1 and 0 when the switch is operated.
An open mind is a virtue...so long as all the common sense has not leaked out.