I see this kind of behaviour probably weekly give or take, I don't spend lots of time viewing the tank sadly so it may be more frequent although I've never seen them actually lock onto one another like your first pic. Definitely a pecking order dispute
I'm not actually proud of owning an obese clown loach, the picture is a couple months old now and they are all on a bit of a diet. Mine go nuts for sinking carnivore pellets which I was feeding a couple times a day along with prima and raw prawn, peas and sweet corn etc etc. But since reducing the carni pellets they seem to have slimmed down some what. Love your clowns mate, both are very individual looking and the big one is particularly nice