Stratix V full reconfiguration only works conditionally

The symptoms of the failed reconfig are very similar to the first one listed in the S5 errata sheet

false configuration failure in active serial multi-device configuration x1 mode

"The failure is indicated by CONF_DONE going high followed by nSTATUS going low and reconfiguration is initiated repeatedly"

except I'm not using a multi-device configuration, and I'm also seeing INIT_DONE go high for about 925uS before each re-initiation

A couple of other observations from today's testing:

I installed SP1 for QII 13.0

Without the additional patch (.23), no reconfiguration worked at all, even when only the sof was flashed. As usual, powerup configuration worked.

I eventually installed patch .24 as well.

With SP1.23 and (1.23 1.24) the reconfig behavior is the same as before.

Something else is unusual: nios2-flash-programmer always erases all affected sectors prior to programming, even if they were previously erased (with --erase-all) or if the data to be programmed should be identical to the flash contents. A --verify option is successful, so the flash can be read and is confirmed to be correct. Is the mandatory erase usual with AS device programming?