Problemas AP WLC9800

[jecheverrif]

Buenas tardes

tengo una controladora C9800 con 23 AP en ella, los AP son  c9120AXE-A, lo que pasa es que 21 de ellos se me conectan a la wlc sin problema y los otros 2 no, la razón por la que no se conectan es " Type of error that occurred last Image-Download" mi controladora esta en la version 

Cisco Catalyst 9800-L wireless controller 17.9.4a

alguno me podria indicar que puede estar ocurriendo con estos 2 AP

Nota; los AP cuando se configuro la WLC se conetaro a ella sin problema, solo hace unos días que vienen con este inconveniente

Muchas gracias

[jecheverrif]

El AP debe descargar la imagen 17.9.4.27 pero se queda en la  17.6.4.56

[Rich R]

Review these guides:
https://www.cisco.com/c/en/us/support/docs/wireless/catalyst-9800-series-wireless-controllers/220443-how-to-avoid-boot-loop-due-to-corrupted.html
https://www.cisco.com/c/en/us/support/docs/wireless/wireless-lan-controller-software/221869-safely-upgrade-access-points-avoiding-i.html
And if necessary (should not be necessary if it still has a working bootable 17.6 partition):
https://www.cisco.com/c/en/us/support/docs/wireless/catalyst-9120axi-access-point/217537-repairing-c9120-c9115-access-points-from.html

17.9.4.27 means you do not have the APSP installed - I highly recommend installing at least APSP6.  Refer to TAC recommended link below but be aware of CSCwj45141  which is an issue that started in 17.9.4APSP8  You might also want to consider upgrading to 17.12.3 which is supposed to have a more robust fix for the image download corruption issue.