Sure! Go for another server. Your server has no business to go slow or not respond or whatever. If it does, it is not worth keeping, especially if that application is of any importance.
If for some reason you do not wish to change servers, then maybe you could just load the .js file on to another more reliable server and add 2 .js links that call the code to each page, each pointing to the same .js file but on different servers. So if one does not load, hopefully the other would. Should work unless there is something in the code that would not make this feasible.