Hello there. I took a look at your working application and found the following:

I loaded your app, everything is fine so far.
I went to the order page and as expected you load the hand model which will take a moment as it is a few Mb in size to load. Once loaded Took heap memory dump ~25Mb.
I went back to the main screen. Took memory dump - still ~25MB
I go back to make new order, there is pause again, took memory dump and as you mentioned it doubles to ~50Mb.

I figured this is something to do with the logic of your web app as it seems to be loading in a new version of the model every time you change a view. I confirmed this by checking the network tab here:

model-rloaded3303×1477 558 KB

Essentially it seems you are calling model.load every time the view changes which is not recommended. Instead you should load the model once on page load (or first use) as a constant and after that only call model.estimateHands().
You do not need to load the model in repeatedly - this will cause memory issues as you have seen if you do not release the old memory using model.dispose(), not to mention it could make your app slow in that moment as the act of loading the model itself is a very intensive process which on some browsers can block GUI updating whilst it loads (our team are actually looking into making the load less intensive but this is not the main issue here - which is the old memory is not being disposed). Essentially the model should be loaded only once and then cached.
If you could change the logic of your application such that it does not load the model on every view change this should resolve your situation.