synchro hubs dont go out of line the triangled shaped dog teeth on baulk ring wear ,replacing baulk rings cures the fault ,its been a weakness of r380 boxes, on reverse gear it self its own dog teeth wear to in the same way .luckily usually the only gear that does ,most boxes need new rev gear too, whine can be gear wear which can go on a long time or worse bearing wear which needs looking at asap