Isn't that a self-correcting problem? If the money supply were held constant, and people didn't invest, then production efficiency would not improve, and there

Isn't that a self-correcting problem? If the money supply were held constant, and people didn't invest, then production efficiency would not improve, and there won't be deflation, right? Even for "risk-free" assets like cash/bonds, inflation risk always exists. It's essentially a risk that you don't have a counterparty willing to trade the things you want.