I see a few people have had issues with lugs cracking or breaking. Mine recently broke, though it was as a result of being attacked rather than a fault in the watch. I did manage a rough repair and, so far, it has been pretty solid.
As much as I love tackling repairs, I'm the first to acknowledge I'm a bit of a hack so if there are more experienced people on here with better techniques, please chip in.
The first step was to melt a platform of candle wax I could use to create a mould. I did this using a toilet roll cylinder and a mini blowtorch:
The next step was to use the good lug on the other side to create a mould for the missing lug:
I then set the watch in place (again, a bit of melted candle wax at the base secured it nicely) and used Q bond resin as a filler where the missing lug goes:
A few hours later I was sable to drill a small pinhole and smooth the rough edges of the lug off with a Dremel. Ideally I would have liked to insert a metal sleeve in the pinhole but didn't have any luck sourcing one.
But, the final result was a useable watch again. I gave it a few sharp tugs to check it was strong and it held up firmly. I've been using it without hassle ever since.
I hope this helps anyone else in the same predicament.
Worked perfectly for me, will see how long it lasts. Thanks for the post. It looks like it is a FR 645 issue.