The fact it is 1st, 3rd & 5th (i.e. all on one side of the shift gate) it sounds a lot like a shift linkage issue, requiring adjustment. I just went through that same thing, but with 2nd and 4th, turned out one clamp was actually a little loose, just enough that the linkage was moving up and down the spline rather than moving the shift linkage at the ZF.
Actually, I purchased #7024 late last year with a '2nd gear synchro' problem and last week after adjusting up all the shifter linkage mechanism I seem to have resoilved any problem it may have had previously Although I haven't driven far yet, it seems to be shifting through all gears just fine, so I'm gonna be real happy if I don't have the expense of ZF repair just yet. Only thing now is I'm toying with still stripping out the transmission, just to check that it has been safety wired.
Julian
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