Max 10 'Downloading ELF Process failed' (on-chip ram)

Using Prime 16.1.2 Standard Edition, after programming a design with a Nios, both eclipse and via the command line, are unable to download the .elf software to the MAX10M50SAE144IX on-chip ram:

Processor is already paused

Initializing CPU cache (if present)

OK

Downloading 53KB in 0.7s (75.7KB/s)

Verifying 00200000 (0%)

Verify failed between 0x20000 and 0x2CC87

Qsys is configured with an on-chip ram of 131072 bytes (0x20000-0x3ffff). Both the CPU and on-chip memory are clocked from an external 100Mhz.

In the Nios BSP settings, I have all code/data segments pointing to this on-chip ram, with the same addresses as generated by Qsys.

What could cause the on-chip ram to not verify?

The other anomaly, which not sure if it's related, but I've set a PLL output channel for 64khz, but instead it comes out as 20khz.. the external input clock (100Mhz) is good .