Student or Learner
Well! Although I do know what ''teethe'' means, I am/was inclined to imagine it (the idiom) as ''something teething with problems'' meaning, thereby, that something is always growing/teething with new problems.
The other meaning that I am inclined to (of ''something teething with problems'') is that it is peppered with/ full of problems.
BUTNow I've corrected my mistake and hope I remember it.