I would agree, it’s more likely that the remote control is broken (even if it emits infrared) than the recorder, because the remote uses a crystal or ceramic oscillator to do its timing.
You may want to try a universal remote that can be programmed for Philips/Marantz/RC5 DCC/MiniDisc recorders. The RC5 codes for MiniDisc and DCC are identical. I recommend the Logitech Harmony series universal remote controls (I’m not affiliated with Logitech but I’ve had one for years and I’m very happy with mine, and I know for a fact that it supports DCC)…
===Jac