If you're going for hardwood idigbo is a bit cheaper than oak, stability is a little better too. Being where the job is make sure they're stormproof & use a good paint system.
Hi Steve, I use the TA450 which should be similar. Above the tilting wheel (at the front on mine) is a locking handle, it's obscured under the tabletop. Try slackening it off & try again, if not it's a strip down & clean.
Get a price on idigbo, cheaper than the oak but dearer than the df. Fairly stable, only trouble I had with a one batch was woodworm but the supplier exchanged it no problem.