WLC 17.12.3 needs APSP 17.9.4?

[Mkvts]

Upgrading a WLC to version 17.12.3 but failed, needs a APSP from 17.9.4?

Improper State./bootflash/C9800-CL-universalk9.17.09.04.CSCwh64998.SPA.apsp.bin not present.

After providing the file installing was succesfull but just for me to know why we need to provide a APSP that has already been installed earlier in version 17.09.04?

Is this because the service pack is applied again or the bug is still present in current version?

[Leo Laohoo]

This is a known bug feature. 

install remove file bootflash:C9800-CL-universalk9.17.09.04.CSCwh64998.SPA.apsp.bin

[JPavonM]

I'm hitting this defect also, but mine when adding APSP1 over 17.9.5 it asked for APSP3 from 17.9.3, and then asking for the same APSP3 from 17.9.3 when adding APSP5 over 17.9.5+APSP1 some time after the first APSP.

Weirdly this is happening only to one WLC out of 7. I've a TAC case open to investigate and clarify how to proceed, and why this happen.

[Mkvts]

I have no access to TAC for this weird behaviour, could you update if you have any news from TAC?

Thank you.

[Leo Laohoo]

This behaviour has long existed as early as 16.12.4.  

The only way to see if the IOS-XE upgrade process has removed old SMU/APSP/APDP is to watch the bootup using the console cable.  

Developers have no interest in fixing this because it has not (yet) reached of "catastrophic" level, i.  e.  not one of Cisco's very, very large customers are affected.  

[Rich R · Accepted solution]

I'm curious to hear what TAC have to say about it.  I've addressed this on previous threads.  The only safe way to do the upgrade is to remove each SMU and APSP individually before upgrade but then you have APs downloading and WLC reloading which is obviously a problem.  The quick fix is:
https://community.cisco.com/t5/wireless/9800-issu-behavior/m-p/4905112/highlight/true#M259614
which clears all SMU and APSP from the install database and reloads the WLC (then APs will try to download the non-APSP code so you might want to shut the AP management interface till the upgrade is complete)!
After that upgrade is clean but this is a very irritating bug in the install scripts!