My friend has experienced a very strange issue with Pokemon Go on separate occasions, initiated randomly while on foot. It started with an unjustified softban that makes Pokemon and Pokestops unavailable (blank tracker). GPS drift could have been the cause, though friend's device is usually quite accurate in this regard.
The softban lasted for about 60 minutes after/during which a shower of repeated captcha prompts occurred. On several occasions there were 10+ of such captchas one after another, despite them being solved correctly. The time between two separate events was no more than 5 minutes and could happen after a couple of seconds. I was present and we chose captchas that were non-ambiguous, such as "choose tiles that contain fireworks", etc. The softban persisted through the entire captcha parade, which then ended for no apparent reason. Nothing helped before that, neither restarting the Android app nor the phone.
Was there ever a known issue with the game that would explain such behavior? Should this even be considered as an issue (is it normal)?
I must say that, in retrospect, it sounds like an exploit used to identify bots as humans by employing an unaware human for the job.
It happened again yesterday during a walk. Luckily it ended after two consecutive captchas this time. Friend said something similar has happened at least five times so far. What is interesting is that my phone has terrible GPS drift and this never happened to me.
We took screenshots of most of the captchas. It started again during a walk at 17:30 and ended an hour later. There were eight retries (17:30, 17:32, 17:34, 17:37, 17:41, 17:41, 18:29 and 18:30). Friend has NEVER cheated in any way, never even had a gym fight. It seems to be getting worse... Below images are in a left to right sequence exactly as they occurred (text is localised, click for full-size images):
Most captchas were "select squares with street signs" and a couple of "select images of bodies of water, such as lakes and oceans", "select images of store displays" and "select images with columns". I'd argue that all of the captchas were solved correctly.