Mitsubushi Challenger - 4wd indication lamp flashing

Wonder if any of you boffins out there can help me.

I have just picked up my 99 Challenger from a supposedly respectable local mechanical franchise after having a service completed, and found that the 4wd indication lamp is flashing while 2High is selected. (ie normal driving mode)
The manual does not make any reference to this problem.

I suspect that the celica-driving mechanic has selected 4wd during the test drive and that I may have some diff lock-up, yet driving in reverse and shifting the selector back and forth whilst driving has not resolved the problem...

Any ideas?

Thanks for your help.

DP