Glad to help!
Yeah, I've had a lot of trouble with triggers in the past as well, they're very unpredictable.
For me, the issue with the movement wasn't specifically having to use up/left/right/down, but rather that the in-betweens make the player stop. Might just be a way that I use D-pads, but it's common for me to keep the D-pad pressed down and simply sliding my thumb to change directions, rather than un-pressing or re-pressing, so as a result, the player would often stop while I changed directions.
Yeah, GB isn't the best when it comes to frame checks. If you haven't already, a handy trick is to put a 3-4 frame wait at the start of update checks so that it only runs update every few frames. I've never used the RTC before, so it's possible it's an especially demanding task.