All the discussion about Peco Jubilees caused me to go to the shed and dig my example out of the small box of "old and not working properly anymore" where it has languished for many years.
A quick inspection revealed the reason it had been put in the condemned box; backwards not too bad, forwards hardly any movement. Upside down on the bench the mechanism runs both ways. Several examples advertised on Ebay have this description, so I suspect the problem might be common to all.
A closer inspection revealed the usual death of many Minitrix mechanisms also aflicted the Jubilee; the axles wear away the cast chassis to the point of non-running. The problem was particularly bad on the front tender axle which had ground its way into the chassis. In reverse the axle is propelled against the plastic keeper plate (hence runs backwards), but forwards it grinds into the chassis.
Can it be fixed ? Yes, though I have a small lathe. Should be possible with a minature pillar drill, but I think someone with only a hand-held minidrill might find this a bit challenging.
So, for those with a spare couple of hours, here's the repair description.
I decided to make new brass bearings, and enlarge the slots in the chassis to take these bearings. Measuring the axle, its a mixed diameter of 2.45mm and 2.9mm, with the smaller towards the outside. Measuring the chassis, its1.8mm thick on each side around the front axle.
With a bit of 1/8" brass square bar (K&S Metal supplies), centred and faced off in the lathe, I drilled an axial 2.4mm hole. Then opened up the first0.75mm of depth to 2.9mm. And parted off at 1.8mm thick (those with pillar drill; suggest sawing off at >2mm thick and then filing back to required thickness). Then made a second one.
Next file away half the material from the side with the 2.9mm hole (thus making a 180degree bearing at 2.9mm dia, and a 360degree bearing at 2.4mm). And finally, very carefully (its easy to splay or crush the bearing with too much pressure, thus ruining it), file the 2.4mm hole to form a slot: I initially slotted the bearing twice with a fine piercing saw and then used various flat and round files to finish. Use a round file to slowly open up the 2.4mm half-hole and slot to nearer 2.45mm and a nice sliding fit on the Peco axle.
Very carefully as the casting doesn't like filing pressure well, and using an old file (because the casting clogs files horribly!), open the front axle slot to 1/8" wide (about 3.1mm), taking material equally from each side. Check the bearings for depth, and if necessary enlarge the slot depth slightly. Fix the new bearings in place with either a spot of araldite or some superglue. Use a bit of 2.4mm round to ensure both are level and parallel whilst the glue sets. Check both give electrical continuity with the chassis.
When the glue has set, file the four tops of the bearings back flush with the chassis castings (only a tiny bit of filing required).
Result; one Jubilee which runs like it should. A drop of lubricating oil and its all finished. Jubilee promoted from the "cond" box to the "runners".