Why are my builders lazy?

Often when I give a build order, the builder stands there for ~2s, and then cancels the order itself. (This applies to builder units and to my commander.) If I give the same order again, it'll usually work the second time, but occasionally I have to give it a third time in order to work.

This happens when the constructor is initially idle, with no enemy units nearby. Sometimes it'll affect the first item of a queue, too: e.g. if I ctrl-w to build several mexes, the builder will stay still for a few seconds, then erase the first mex from the queue and go straight to the second.

What could be causing this? It seems like some widget should be the culprit, but it doesn't seem to fit with the "use idle engis" widget or the "dynamic avoidance" widget. It makes it a lot harder to play, as every time I give a build order, I have to watch the builder for a few seconds to make sure it is complying.

sometimes if you queue up buildings, i also made the experience that they get cancelled. but there are conditions, which cause this.

if you queue up too close, the second (smaller, e.g. a lotus) building may be allowed before the first building (e.g. a lv fac) was completed, but later it is disallowed and therefore cancelled.
second thing is a timeout to try to complete the queue, e.g. if the con cant reach the building site or the site is blocked by an allied unit which wont clear the site.

but nothing like your story ;)

This also tends to happen to me often actually. I have no idea what's causing it.

Probably dynamic avoidance with an enemy close. Or autoreclaim or autorepair where the con rather repairing something first.

maybe there's something wrong with autoreclaim widget or it conflict with a similar widget of different name IMHO.