It can be a lot of things, but it's definitely a common problem with 10/22's. I have a volquartsen deluxe that will throw the first shot same place outside the other 9 every time, tried all sorts of different ways to chamber the first round, 5 rounds in mag, different ammo, etc. never have fixed it.
In a stock 10/22 bolt some feel the firing pin can raise up and cause inconstient ignition, others feel it's a less than square bolt face, either combine with hand chambering the first round to cause an issue.
I've heard of no less than 5 ways one should chamber the first round in a 10/22 and all of them appear to fix the issue for some users, and do nothing for others.
1) Leave the bolt closed, insert mag, rack handle as fast as possible
2) Leave the bolt locked back, use bolt release to close bolt
3) Leave the bolt locked back, slingshot bolt closed
4) Leave the bolt locked back, ease the bolt forward
5) Hand load the first round into the chamber, ease bolt closed.
If you are loading 10, some feel the extra mag tension of the 2nd round impacts how well the bolt closes
Some will say depending on the ammo and rest period between groups the lube/wax cooling messes up the first shot ( I have seen this first hand, some ammo is worse than others )
Along that line is that some get frustrated with bad groups when switch between ammo, when you switch between ammo for groups with different types of lube etc. you may need to fire 5-50 rounds to get the new lube/ammo to settle down. This is probably one of the biggest mistakes I see people make when testing out different .22 ammo brands at the range.