Had similar on a later shimano free wheel that wasnt 'catching' properly.
Threw loads of WD40 in it, bounced the back wheel up and down to jolt it a bit and then got stunt double son to ride it round the block for a while to free it up, kept slipping and he was told to jolt the wheel as i'd done. eventually it freed up and worked properly again.
I think what im trying to say is 'mild abuse'
Youll get a sensible answer soon
[size=75]1959 Mercian King of Mercia Roadbike - awaiting some TLC
? Orange Clockwork - Daily rider - awaiting some TLC
1984 'Alpine' Main Battle Tank Roadbike - Claimed by the Son
1993 Holdsworth White Moss MTB - Not seen another like it
1994 GT Outpost Trail MTB - Project 'War Finish' - Consigned to the shed
1995 Mongoose Menace BMX (Bitsa.. Mongoose/Db/DK) - Son's Skatepark Bike