Replace door awning motor cap by identifying awning brand and ordering from RV parts supplier or manufacturer. Protect motor end from moisture until replacement arrives. Most caps snap or screw on.
Several companies specialize in rebuilding Oasis RV heaters, including RV Parts Country, Suburban Manufacturing, and local RV repair shops. You can also attempt basic repairs yourself or consider upgrading to a newer heating system.
Oasis tankless needing daily reset likely has a control board relay issue. As a workaround, install a timer to auto-cycle power each morning, or plan control board replacement.