Hotspot UAM login is slow on Android

[mr_arsyad]

I noticed that on Android logging in via hotspot is slow and can take up to 30 seconds. On iOS, it only takes 2 seconds at most.

However, if I manually log out from the Wi-Fi by visiting http://10.1.0.1:3990/logout and login again, the login is fast, same time as iOS. Then if I disable the SSID and enable again. Login is slow again, unless I visit the logout URL. This is very easy to replicate on my end.

R500, standalone. Firmware - 100.1.0.0.194. No controller. Hotspot settings doesn't affect the results above. But just for discussion, my settings are nothing special:

1) Setup a SSID with hotspot
2) Packet Forward is "Local Subnet NAT and Route to WAN"
3) Local Subnet: Local Subnet 1

Under hotspot, the unauth URL and RADIUS IPs are on the cloud and all walled garden are set correctly. I set my URL to www.google.com after successful login in the hotspot settings. The rest are default parameters.

I can see the unauth URL loaded. Once I try to login, the script of the page will bring me to http://10.1.0.1:3990/login?username=myusername&password=mypassword.

This is the part that takes some time as per above. Only for for Android devices.

I also tried Chrome remote debugging via USB and also saw that after visiting the login URL above, the AP tries to redirect to the success URL (i.e. google.com) but with a status error "ERR_QUIC_PROTOCOL_ERROR" and type as pending. After about 30 seconds or so, the success URL loads.

Are there settings that affects only the Android devices? Or is this a firmware issue?