A590 FastRAM Errors

[Sim085]

I have bought around 20 chips from China to use as FastRAM for the A590 (HYB514256B-60 SIEMENS 256 K x 4-Bit Dynamic RAM). Lucky me managed to find 4 working ones out of the 20 received - enough to configure the A590 to run in 512KB mode.

The majority of the Chips outright did not work, yellow screen or started booting and then system crash half way through the load. However I had a couple where everything looked to be working fine but Amiga Test Kit reported errors after for example 10 runs.

I have no experience with these chips.

Am I correct that any error (yellow screen, crash, or errors reported by Amiga Test Kit) mean throw away?

Also, anyone know any good source for these Chips? Or I should keep ordering from China in bulks of 20 until I get another 12 working ones?