does this happen when the trailer is plugged into shore power or when it's NOT plugged into shore power?
and does your trailer have a battery disconnect switch?
if it's not plugged in and you don't have a disconnect switch, then the trailer's normal parasitic power drains are the probable cause. especially if you have a single battery.
you'll have to keep it plugged in or get a disconnect switch installed.
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC