AvatarNathan Richer

I had a similar problem where every morning i would wake up and my flexor hallicus would be tight, and sometimes my anterior tib would also be tight.  both served to tighten up tissues around my ankle in the morning.  subsequent mobility work pre-workout would loosen it up enough for a good workout to happen. but then it would repeat the next morning!

what made it better was actually tib-fib taping.  apparently due to multiple ankle sprains over the years, i started having a tib-fib problem where the mechanoreceptors in/around my ankle were messed up due to the damage of sprains and healing up with scar tissue.  the receptors could not figure out how to fire the right muscles in response to normal every day things from standing to walking to running.  i finally did taping every day around the ankles for about 2 months and this calmed things down A LOT.  
it’s not 100% unfortunately, but it is a lot better.  I still tape for workouts and taping brings almost immediately loosening of my flexor hallicus and calf structures – they respond better to mobility work and smashing and remain loose for the rest of the day, even after i take the tape off after the workout.
this may or may not be your problem but i also had very locked up ankles as a result.  also not sure if i would recommend this, but my chiro PT showed me how to release my ankles using a self manipulation.  that also helped a lot and i do it to both ankles after some band mobility work.
if you want to give it a try to see if there is an effect, get some sports tape (highly recommend Johnson & Johnson brand, do NOT buy any other brand- trust me) and some pre-wrap.  wrap the pre-wrap around your ankle, right above your malleous/ankle bone.  Then wrap 2 circles of tape around the pre-wrap as tight as you can get it without cutting off circulation.  Keep the direction of taping in mirror images to each other on each ankle.  then go mobilize and smash and test to see if it is better. 
another thing to try after this is to tape before bed at night and leave it on all night, and then get up to see if you still have a locked up ankle.
if it is better, you might try taping up before each workout, or go for a full 2 month/every day taping protocol…