WPS error msg=12 when trying to connect

Installing and Using OpenWrt Network and Wireless Configuration
1

I am trying to connect to WiFi repeater to my OpenWrt router. The only way to connect it is by using wps. I followed the guide here and set up wps on my OpenWrt device successfully (I think).
However, I can't connect the repeater to my network. During pairing, I can see the following error message in the hostapd_cli logs:

<3>WPS-ENROLLEE-SEEN MAC:ADD:RE:SS
<3>CTRL-EVENT-EAP-STARTED MAC:ADD:RE:SS
<3>CTRL-EVENT-EAP-PROPOSED-METHOD vendor=0 method=1
<3>CTRL-EVENT-EAP-PROPOSED-METHOD vendor=14122 method=254
<3>WPS-FAIL msg=12 config_error=0
<3>CTRL-EVENT-EAP-FAILURE MAC:ADD:RE:SS

Google has failed me, so I am hoping someone here has any ideas.
My network config just in case:

config wifi-device 'radio0'
	option type 'mac80211'
	option path '*****'
	option channel 'auto'
	option band '2g'
	option htmode 'HT20'
	option country 'DE'
	option cell_density '0'

config wifi-iface 'default_radio0'
	option device 'radio0'
	option network 'lan'
	option mode 'ap'
	option ssid '*****'
	option encryption 'sae-mixed'
	option key '*****'
	option wps_pushbutton '1'
	option bss_transition '1'
	option ieee80211k '1'

config wifi-device 'radio1'
	option type 'mac80211'
	option path '*****'
	option channel 'auto'
	option band '5g'
	option htmode 'VHT80'
	option country 'DE'
	option cell_density '0'

config wifi-iface 'default_radio1'
	option device 'radio1'
	option network 'lan'
	option mode 'ap'
	option ssid '*****'
	option encryption 'sae-mixed'
	option key '*****'
        option bss_transition '1'
        option ieee80211k '1'