Thinkpad T420 suddenly won't turn on. Only turns on occasionally

[madbot]

Suddenly the laptop just wouldn’t turn on most of the times I press the power button. On the times it did turn on, only twice did I get a “0187 EAIA data access error” and a “2200: Mahine Type and Serial Number are invalid.” Those errors have not appeared since

Turning on the laptop, the system clock would be out of sync. A windows update and replacement of the back up battery seemed to have resolved this. However, the original issue still persists. It only turns on occasionally when the power button is pressed.

I’ve tried doing a power reset but to no avail. Turning it on without the battery and only the charger, I just get three rapid blinks from the battery light indicator. Turning it on with the battery and charger, I get three short blinks, one long blink, then a short blink on the battery light indicator. Would this be an issue with the motherboard or EEPROM?

Extra info: No major upgrades or modifications have ever been done on the laptop save for upgrading to an SSD and adding one more stick of RAM. I've already tried reseating the RAM, and booting the machine using only one of the RAM slots at a time but still no luck

[deickos]

sometimes this erratic behavior is caused by humidity - once i restored another thinkpad with such issues by removing the kb and putting it in the oven at 50 celcius
you have to keep it in a plastic bag if you don't use it often