Did you re-flash the stock firmware? If so, then it's most likely not the programming or firmware.
The RAMBo is a circuit board, and components on circuit boards can go bad. If that happened to components that directly affect the LCD pins, then you'd have trouble.
You could try replacing the RAMBo board to logically determine if that's the problem. If you do and you still have the same problem, you know the problem is elsewhere. But given the other troubleshooting steps you've tried, that is possible.
i often use 600 grit sandpaper to get burnt plastic of the sides of my printer nozzle. By doing this filament is less likely to stick to nozzle and drag across your print. Of course you can always soak in Acetone however that is a long process of waiting.
There's multiple setting in firmware that causes the print head to disable at temperatures higher than 240ish. Go into the updated firmware supplied by seemecnc and in the master config file in Arduino use ctrl f to search "temp". youll notice some max settings are set to 240. change those to 270. even though he280 can go slighter higher im not familiar with any filaments that require that high of a temp.
And I guess that a delta machine is always noisier than a Cartesian printer because it runs all 3 motors all the time. I think the firmware has some kind of an impact. I remember that the Prusa MK2 has different run modes in the firmware settings that impact the noise level. Running the motors in the low power mode makes the printer very quiet. I wonder, if that can be done on a Rostock, possibly by using Marlin instead of Repetier.
It sounds like an issue with the power supply. If you purchased through MatterHackers, please send an email to email@example.com and we'll assist. If you purchased elsewhere, please contact SeeMeCNC: https://seemecnc.zendesk.com/hc/en-us/requests/new?
I had a similar issue occurring. It was frustrating on long prints. The problem has been resolved for me and I think it was several issues occurring for me. I tried many things to resolve it including new Bowden tube types as well as the "grabber"
One was to much pressure building up within the extruder. Reducing the flow control can help here. When your temp drops you may be experiencing this. Have you tested your thermistor and are you sure you have the right thermistor defined?
The second for me was the Bowden tube did not have much slack for prints that were at the extreme of the radius. This caused it to slowly work its way out over time in long prints. Using a longer Bowden tube help resolve that.
The accelerometer error is being reported by your printer's firmware. I'm guessing you did a firmware upgrade as part of your E3D installation. It sounds like whatever firmware you put on your printer is trying to use the accelerometer and is throwing the error because it cannot find it. There should be some way to disable this in your firmware configuration.