Is your watch a recent purchase, or have you owned it long term (i.e. several months/years)? The crown coming loose is a small and trivial issue; it can be threaded/tightened to the stem, however the stem itself would need to come out to do so. The movement stopping overnight is obviously the bigger issue; you mention that it is a problem that has only recently surfaced, so I presume you've owned the watch for some period of time (long enough to notice it as a new problem). It might be a good idea to get the movement serviced as in general there's no telling what kind of condition or age the movement was in when it was cased up during assembly. An overhaul should remedy whatever the problem may be (which could be a number of things, ranging from something as simple as hands coming into contact with one another or a dial marker to a worn out mainspring, etc). If the watch is a recent purchase, maybe contact your TD to see about getting the issue resolved in that manner? Most are receptive to helping when troubles arise...