Sounds like trash in the lines. Somewhat common, sorry to say. It moved over night, but will never come out. Could be plastic, sawdust, metal shavings, or something else. Its a slow process, disconnect each line at the fixture, hook a jumper hose to it, and aim out the door, pressurize system, and see what come out. Let pressure off, change lines, do it again. Bathroom has 5 lines. If it is new, I would take it back if feasible.
I still don't get why people would buy a trailer without a good PDI. Water working, fridge cold, water heater, AC/heat. Our boss makes us all but camp in one before we tell the customer it is ready.
2012 Ford F250 ext. Cab 4x4
2002 Jeep Wrangler Sahara
2008 Yamaha V-Star 650 Classic
2008 Work and Play 18LT