I used fracker on the portal, and after only four hacks system said that portal is overheated.
I have a video where showed time of fracker using, present time and message of portal's over-heating
Not a bug. Normal burnout rules (4 hacks within 4 hours) still apply even with a fracker. The only thing a fracker does is doubling hack output for 10 minutes or 150 hacks on the portal from all agents around, whichever comes first.
To use a fracker most efficiently, you'll need to install Multi-Hacks so the portal doesn't burn out after 4 hacks.
@Zlatolist, Portal Frackers only doubles the portal’s hack yield for all agents. Also, a Portal Fracker lasts for 150 hacks by any agents or 10 minutes, whichever comes first. You may check out this link for more insights. That being said, I'll be closing this. Do let us know if you need help with any more questions. Thanks!