Pulse commands intermittently fail to turn off

I would be most grateful for ideas on what is the cause of some very odd (but intermittent and therefore tricky to diagnose) behaviour that I have noticed in my Cbus setup.

The system was installed in about 2010 and has performed flawlessly until recently.

I have a mix of 19 units wired in a star configuration including a B&W CTouch unit that mainly does scheduling of hot water, blinds, underfloor heating and some logic that handles towel rail, extractor fans etc.

The programming and logic of the CTouch have not been altered since 2019. I have made no other changes to the network in many years.

Over the last 6 months or so I have noticed that groups that are controlled by pulse commands occasionally fail to turn off. This seems to happen most often with groups that are pulsed on for longest. The pulse commands are all issued by the B&W CTouch unit and all control groups that reference channels in a 12 channel DIN Rail-mounted relay unit. I have not noticed any problems with groups and channels in this relay unit that are controlled by other input units. Schedules that issue "On/Off" commands (rather then relying on a "pulse for X hours") are similarly fine.

Initially I suspected the CTouch unit and, as I had a spare with identical programming, swapped them over. The problem persists.

I have attached some screen shots from the diagnostic utility. All units ping and pass a reliability test. The only exception is a one channel relay that isn't reporting its voltage or firmware version (but this seems unrelated to the problem). The traffic analyser shows occasional errors when scenes are triggered from the DLTs.

Today I noticed that only 2 units had their CBUS clock enabled and as the recommendation seems to be 3, I enabled the clock in a third. I will see if this makes a difference.

Power supply issues seem to crop up frequently in ageing systems and my initial suspicions were with these. The network is powered by the integral supplies in 2 Din-mounted dimmer units. However the unit voltages are all over 26 volts. I can persuade myself that the green "Unit" LED on the front of one of the power supply containing dimmers is less bright than its counterpart. I was on the point of replacing these units but without expert advice or more evidence of PSU problems it seems an expensive long-shot.

Whilst I can sort out some workarounds to avoid the use of pulse commands or catch their failures. I am wondering if this is an early symptom of something else.

Has anyone seen this before and any clues about what is going on?

This forum has been a fantastic resource in the past and I look forward to your advice.

Phil