Yes your situation is exactly what I meant.
So the problem right now is that you are load-balancing. So if you're lucky your packet is NAT'ed towards the IP of WAN2 and sent outbound that way. So for as long that flow exists the page will be reachable.
However another time it's possible you get routed out the WAN1 port.
The MX will not take into account the IP subnet located at WAN ports when NAT'ing your packet. So normal routing will not work. Yeah I know, weird right.
So you have to actually configure the MX for IP traffic going to the 192.168.1.0/24 subnet use WAN 2 uplink.
So in Dashboard go to Security & SD WAN -> SD-WAN & Traffic shaping -> Uplink selection and add an internet flow preference. It should be obvious from there on.