I've had this happen or anticipated it happening myself. It may be that your row gauge rather than stitch gauge was off and that is the source of the problem or it could be a problem with the pattern itself. I assume that you need to get in a certain number of increases before the end of the sleeve. Depending on how many increases you need, you could rip out the last few cms and put in some more frequent increases or, if you decide to do the sleeve again, increase the frequency of the increases (say every 4th row instead of every 6th row). See what frequency will get all the increases in given the row gauge that you measure on the current sleeve.
Yes, 29cm from the shoulder is the length of the sleeve. If there's a schematic, you may be able to confirm that on the drawing.
ETA: I just re-read your post on the raglan sleeve sweater in which case it may be decreases that you want to get in within a certain length but approximately the same advice holds true. Row gauge is more important here than usual.