Braked connection through ssh may have many causes.
It can be some damaged hardware on ROSbot (antenna, cables or WiFi module) it is easy to check. Please connect your ROSbot to display, and ping some external server. If you didn’t see any issues it’s mean that problem is somewhere else.
It also can be problem with too many WiFi networks, devices etc. in the same channel.
You should also try to connect ROSbot to another network (different AP) to rule out a hardware problem between those two devices.