IP: so far seen from 79.116.242.abc and 82.76.59.abc (both Romania)
UA: Mozilla/5.0 (compatible; Jetslide; +http://jetsli.de/crawler)
UA: okhttp/3.9.0
Referer: http://jetsli.de/crawler
robots.txt: no
Pattern: sets of 3 involving one page, one IP each time
HEAD /somepage/ with jetslide referer and UA
GET same page with okhttp UA, no referer
GET same page with jetslide referer and UA
Both IP ranges claim to be residential but I kinda think they're really server farms. Middle of 3 requests is of course blocked (headers reveal three deficits in addition to bad_agent).
The two pages requested to date--one in early August, one recent--suggest it is following an RSS feed, but so far isn't doing so religiously.