Unfortunately it tends to do so randomly (was using foot for like 3 or so years by now). And in the end you'll only ever end up saving single digits of RAM. I suggest using server mode *only* on a RAM constrained device like a SBC or a embedded device (Tablet running Linux).
I use it this server-client mode for a couple of months at least, and I never experienced any crashes. Not that I see a huge difference, just it fits my workflow better. I do have many many terminal windows open at the same time, but most of them aren’t busy doing something. They are either some kind of app (e.g. ranger) or a space I usually come up to do something specific (e.g. this workspace I use for sshing that server and that workspace to do things locally).
PS: i am issue number 3 hueh