The PanelView Plus 400 & 600 Base Units are indeed fixed hardware units and not modular like their larger siblings, the PVP 700 - 1500. I've posted this image before here on the Forum for reference...
If you have a "3a Stuck Touch" POST error or the "no touch picture" (Stop Hand) after a power cycle of the terminal, then there is either something depressing a section of the display touchscreen or it is faulty.
When you boot, and POST is executed, and the fault on the touchscreen is present, POST will detect this as a stuck touch cell or cells and display the "3a Stuck Touch" error.
If you power cycled at some point, and then only received a Stop Hand indicator, then this would suggest that the touchscreen fault had temporarily subsides during POST and allowed the terminal to boot. Only then do you later see the Stop Hand indicator when the touchscreen fault reappeared or the touchscreen was attempted to be used.
When you power cycled and got, or are still getting, the Stop Hand indicator, what is the terminal doing in the background? Is the application loading? Or is the terminal at least booting as far as the application Load and Run options? If so, then while the terminal is at one of these status, you could attempt a backup transfer via cable from your workstation PC using the METU (ME Transfer Utility).
Does any part of the display look scratched, dirty or otherwise damaged? Is there an anti-glare membrane fitted? Have you tried cleaning the display while powered off? Also, pressing gently but firmly all around the display can sometimes help to release a stuck cell or two, but not always. It may just be faulty and in need of repair/replacement.
Regards,
George