Hmm, I'm normally hitting level 3 at around the time of reaching the grove for the first time. And from checking a couple of my old saves I can see that it should take 300 XP to get to level 2 and 900 to level 3, in line with the 5e table, so your 50 to go to level 2 does sound weird.
Unfortunately I've no idea what might be causing your issue or how to fix it, my only suggestion would be to submit your savegame to Larian support to see if they can help. You can attach your zipped file if you use the feedback form on the launcher, which automatically puts in your game version number, or via the support site at
https://larian.com/support/baldur-s-gate-3#modal.