after owning a B-6000 for 26 yrs,I have found that the rubber under the steering wheel to be a bad design.
most kubotas have this problem.the best solution(to keep it from happening again)is to drain the oil out of the gear box and replace it with a grease fitting(in the hole where the oil goes).You can drill a small weep hole in the side of the gear box to flush out any water.it also dosent hurt to pull the steering wheel and put grease on the rubber bushing every so often.it ony took me once to find this out(20 yrs ago)been running grease every since with no problems.