Why so many PA issues on Class 318/320/334?

[Scotrail12]

A good chunk of the time, the PA on these classes of trains aren't working (especially 334) and I've noticed that the PA system on 318s and 320s tends to stop working if coupled with a 320/4 and even the display screens on the outside don't work either.

Secondly, I've been on two 318s today on different routres and the PA system is completely different - they no longer have announcements telling you the next station and the announcement for Wemyss Bay at Central is significantly shorter and skips through some information. No info on the next stop but plenty of info about passenger information notices around the train.

Why are there issues with the PA on these 3 classes so often? 380s and 385s never have any issues nor do the DMU's.

 

[Scotrail314209]

A good chunk of the time, the PA on these classes of trains aren't working (especially 334) and I've noticed that the PA system on 318s and 320s tends to stop working if coupled with a 320/4 and even the display screens on the outside don't work either.

Secondly, I've been on two 318s today on different routres and the PA system is completely different - they no longer have announcements telling you the next station and the announcement for Wemyss Bay at Central is significantly shorter and skips through some information. No info on the next stop but plenty of info about passenger information notices around the train.

Why are there issues with the PA on these 3 classes so often? 380s and 385s never have any issues nor do the DMU's.

I've noticed if the 318 or 320/3 is leading with a 320/4 coupled to the rear, it'll display the calling points with nothing being displayed on the 320/4.

However, if its the opposite way around the 318 will simply display the destination without the calling points. I also think they altered the text on the 318 and 320/3 screen to match that of the 320/4, but the systems seem to be completely different...

It's more prominent on the 320/4 where you have 4 things:

1. The announcements will work
2. The announcements will work but at a barely audible level
3. No announcements, just screens
4. Nothing at all.

The 334 have a load of issues previously, one of the most prominent being when the system would glitch and Fletcher's voice would pitch down and sound very distorted. Example here:

Another issue I remember is when the PIS would go absolute haywire on the approach to Springburn while working a service to Cumbernauld. It has been known to jump back to a random station, one I remember the most was on a 318 and it suddenly blurted out that we were approaching Yoker.