Error 503 Backend fetch failed to grid/users/reviewer-select/reviewer-select-grid/fetch-grid

[Glauco_Roberto_Munsb]

something similar by @alexxxmendonca at this topic Reviewer list won't load (OJS 3.0.2.0) - #5 by alexxxmendonca at the same line, but my issue not show any json_encode() or other info.