I tried CoCo parent set; with "Crazy Painter.CAS". Typing "cload" or "cloadm", a black rectangle with seemingly random letters and numbers appears, then disappears and a message "IO error" appears.

What I meant by the RAM having no effect was that changing it did not effect loading ROMs "Arkanoid" and "Malcolm Mortar" freeze at a black screen, and loading discs "pacdude2.dsk" and "Zenix.dsk" start to load, then freeze at a screen with scrambled graphics.