Horse dropping hind in trot

[jord.nc]

Hi all,
Looking for advice / suggestions regarding what is going on with my mare. In trot, more so in arena, is dropping a hind leg every so often.
I have had vet out, who has advised it would be difficult to assess lameness when it is so sporadic and in between episodes, appears sound.
I have her on Boswellia for anti-inflammatory purposes and I often use magnetic therapy.
Any advice greatly appreciated!

 

[nutjob]

Get some video footage of it from different angles and then get a better / different vet on the case. A physio workup might pin point any pain or range of movement issues in the meantime which can help a vet to come to a diagnosis.