En-route, at roughly FL220 during the climb with the autothrottle engaged, the autothrottle began to make sporadic inputs from its intended N1 (in magenta on the EAD display) to IDLE. Since then, it began to increase from IDLE apparently attempting to go back to its intended N1 power setting, to then idling the throttle once again. This constantly continues even with the autothrottle disabled, rendering my manual inputs to the throttle useless. It is key to note that the throttles are moving to accompany the fluctuating power settings with the autothrottle enabled, however, if I disable the autothrottle and apply full power, the throttles themselves remain in the full power position, yet the engine power fluctuations still occur.
Hardware rendering WAS enabled.
The displays themselves (engine display AND PFD) appear to be very laggy, with a significant delay to the PFD displaying a change to pitch or roll and to the engine display in showing power settings. I've attached a GIF to show the display lag and power fluctuations.