Yes have this as well on PC, remember it being a bug about 3 years ago or so on the first TSW. All AI have 00000 (apart from the coaches)
This has been fixed and then broken again multiple times. Similar issue with the Mk3s, they used be A,B,C and so on. Now they are all coach A and just L at the end. The Mk2 coaches used to havve proper running numbers, and since TSW 2 they are all numbered 12345.