Asus 4g-ac68u - in LTE + WAN mode - tls handshake, breaking broken movies

Hello.
the 3rd week of the fight with the router begins.
I wanted this model because it allows you to connect the internet from the WAN and LTE port in load balance mode.

I tested on LTE from Play and T-Mobile. wan like a wan, it worked without any problems.

now the thing is that when accessing the website (with firefox), the inscription that the TLS handshake is in progress is visible for a very long time.
on other browsers it takes a long time to start up so it's not a browser issue.
streaming movies don't start or not.
speedtest.net shows either a very nice connection - 80% of the time. or connection error: could not connect to internet. please check connection and try again. I'm using the desktop version.

I will add that it is the 2nd copy of the above-mentioned router so 2 operators, 2 copies. apparently a very good router but maybe nobody uses it in this way
I reported it to the operator of both. I replaced the sim cards.

I'm in the middle of giving up. unless there is someone who will help me
greetings.

edit: it looks like this router just can't handle load balance. standalone bath or lte works approx.
maybe someone knows the secret of this router?

What is this loadbalance for? If you wanted such things, OpenWrt on a properly efficient router would probably be better.

load balance combines bandwidth with LTE and WAN. when i do speedtest it even works. well 80%. because in others the page is not loading
I don't know enough to do something like this myself.
generally. lte or wan flies by itself. on load balance problems.
I found some posts from slightly different types of routers where they say that something like this can't work well because there is no consistency in ip addresses from two operators (lte and wan) and servers go dumb.
well, they added such a function in this router ...

http://www.tomshardware.co.uk/answers/id-3190468/setting-dual-wan-lan.html

Added after 1 [hours] 36 [minutes]:

I will add that I would be tempted to an alternative. but I found nothing.
maybe OpenWrt, but it would have to be wifi and 4th lan on the router.

Added after 14 [minutes]:

I will add that I already have enough of this router also because any change is a restart that takes 1 minute and 20 seconds.
even quite banal changes ...