Bosch Maxx WFL 2450 Drum spins once and then stops

“Machine did not complete spin cycle on last load and but it did spin when put on a spin only cycle”
3 simple things to check 1st and why. 1) the machine might have failed 1st because it did not pump out properly / fast enough, but because you then tried it on spin only the extra time allowed the machine to pump out = then spin. The machine has to pump out 1st before it will spin so check that and see point 3. 2) this is an old machine. When were the motor brushes last changed? Do you hear any low key crackling noise when the drum / and so, the motor turns esp on spin? Possible that the brushes have almost completely worn out is the point. 3) inverse blockage in the air trap = machine fills to a more than normal level but cuts off ( which is a bit of luck otherwise you get very moist! ) and will do the wash cycle just fine BUT when the machine pumps out the compressed air in the pressure switch hose cannot escape = the actual pressure switch ( abv: p/swt ) contacts cannot be detriggered = in other words the p/swt thinks you still have a tub of water inside the machine when you have not and so will not spin….however what can also happen is the trapped air eventually escapes allowing the machine to then spin after X minutes. With an empty machine with the power off take the p/swt hose off the p/swt get a cup of luke warm water take a big gulp and blow the water down through the hose. Any blockage doing this is usually pretty obvious. Motor brushes. 2 types fitted to your machine. The most common set is part number 154740 and there are cheaper pattern versions aplenty but any of these are a bit fliddly to do and the much rarer Siemens motor whose brushes are part number 173028. Hopefully, if required, you have the former set as the Siemens ones are not cheap.
If it is non of these pointers you are probably going to struggle.