Just reading an old 1970 EMER relating to the No5 and bayonet to the effect that some left hand bayonet grips were manufactured to a defective drawing, that were .017" undersize in thickness and therefore making the counterbore for the nut too shallow. These grips were also .015" too narrow/width which would require excessive adjustment to the right grip. Units having these undersize grips should scrap them and demand replacements.
Two points here. If you have a) a dodgy left grip, that's the reason, b) it mentions that the left grip should contain the nut - if you were even unsure which side the nut/bolt should go and c) it only mentions the nut as oppose nuts..... So this might (?) indicate that the problem was only with early single screw grips.
And here's something else. It mentions a SCABBARD Assy, Mk2. I always assumed that this related to the pressed/folded/wrapped steel mouthpiece, but not so. According to the EMER, this scabbard
'.........differs from the Mk1 only because of changed spring and mouthpiece design. The spring is made in two parts differing only in that one (of the springs?) has a hole for the securing screw and one is dimpled to locate in a hole in the mouthpiece. After assembly of the springs and mouthpiece a securing screw is fitted which locates the spring which is drilled (to allow the screw to thread into the mouthpiece...?). The thread in the mouthpiece may be 6BA c/s screw or self formed by a No4 self tapping screw
I've never seen one like this and nor has my pal, the senior examiner! The closest sort-of offering I recall is from a long Indian scabbard. If YOU have one, please let's have a photo. Apparently the actual scabbard is identical. Whether your No5 or L1A1 scabbard has a flat bottom or fully tapered is simply a manufacturers allowable variation.
And if anyone's really interested, the price of a No5 bayonet in 1965 was £2:90p and a scabbard £.50p.
A No9 bayonet £2:20p
No7 bayonet (several prices listed £3.90p
L1A1 Bayonet £1:25
L1A4 bayonet £3:75