Here's a known list of glitches in Google Santa Tracker sorted by minigame. This only includes glitches that affect gameplay. Visual glitches are not included. All glitches included are present in the web version of GST. The webapp may be different.

Wrap Battle Wrap Battle is VERY broken and most of the glitches here were found by and directly copypasted from TplaysTouhou, shoutouts to that guy. -The notes for Level 3 & 4 play slightly earlier than the music -The rate at which you get points for hold notes is tied to frame rate -Increasing frame rate also increases how quickly you lose the white multiplier -Dropped frames help keep the multiplier gauge from draining -When you pause and restart, any notes on the screen get erased but can actually still be hit after the score is reset to 0 and probably many more that my puny brain is too small to comprehend

Santa Search -After completing a level, pressing the red restart button will bring you back to the level select screen, but the game over menu will remain -In the Beach level, Mrs Claus may sometimes be missing. She is still there and you can 'find' her by clicking above the green elf at the entrance of the beach hut, in the gray area. Take a look here:

Present Bounce -In Level 10, the top of the chute has no hitbox and you can insert springs and conveyors through it. This is used in world record runs to make Level 10 easier. -You can jam conveyors between other conveyors and the candy-cane shaped pipe things to push them inside of pipes (This was a bad explanation. Look at this:) -If you stick a conveyor or spring in the bag where the present is meant to go, you will not be able to eject any presents, softlocking the game. Pausing and unpausing will re-grant you the ability to do so, but you don't advance to the next level when the presents go into the bag.

Build and Bolt This entire minigame is pure jank. -Penguins sometimes only have hitboxes when the arrow keys are not being pressed at all -Rapidly clicking the green 'Next' button will allow you to skip levels -Restarting multiple times quickly allows you to take control of the player before the countdown is over and way too many more that you will definitely experience playing it

Map Quiz -Attempting to click and drag on an already placed country will make all unplaced countries unmovable, resulting in a softlock

And that's about all I remember so far.