Front intermittent lameness

Hello!
I have a 16 yr old QH, that I’ve owned for a few years now. He has a pretty simple work load and had about 3+ months pretty much off with a few scattered light (walk, trot) rides due to the weather being crummy. We started getting him back into work about 2 months ago and since then has had two instances where he came out lame on the front right. We had the vet come out to look at him and he saw the lameness, he performed a flextion test to which he flexed negative in the front and a little in the hind. The vet suggested we do his yearly hock injections a little earlier this year. After getting his hocks done he felt amazing! Today (about 1 month after his hock injections) he came out lame at the trot on the same front leg.

I’m hoping to get some advice on what I can look into and ask my vet about.
I’m waiting on my farrier to come and hoof test him and see if he sees anything. (He was just shod 1.5 weeks ago) I’m also thinking of running bloodwork for lymes and vitamin E.

Anything you guys have to offer will be very appreciated! Thank you!

A lameness eval should include nerve blocks and hoof testers (unless the source of the lameness is obviously not in the hoof). That is pretty basic order of operations for a lameness exam.