wep turns into wpa

Hello everyone,I didn't know whre to write this question and please excuse me therefor.

The thing is I tried to crack an wep encrypted router and when it start to collect the IVs it automatically turns on wpa encription.

When I restart the airodump-ng with the bssid it comes again in wep encription.

Is there any solution how to fix this with airodump or aireplay?

Thanks for the answers.

What wifi card are you using and chipset.It sounds to me like a driver issue.

Have you tried another wifi device besides that one causing you the wep to wpa switch?..