When I travel to the cave containing the Enhanced Wolf boots diagram, I can't open the chest. Sometimes it will glow when I use Witcher vision but when I approach it I have no option to open it and the Witcher glow disappears.

I have tried meditating and also reloading the game, but the chest still wont allow me to open it. I did a little googling and it would seem that others have suffered from this bug too.

It's a little frustrating because this is the final armor diagram that I need to collect.

Any suggestions / workarounds that I can use?

I will start by recommending the "standard" solution:

Your game installation could need fixing. If you use Galaxy try using the verify/repair installation function and see if that helps. Also try removing any mods if you are a mod user.

When you got to the Grotto, did you interact with the witcher symbol on the rock outside the cave?

Thanks for the suggestions guys, I will give both a try (I honestly can't remember if I interacted with the wolf symbol before going in, but I will give it a go)