Non-periodic Switching in Forced Cont. Mode

Hi,

I use LTC3810 for 28V input 12V output 450khz and 40w output power. I limited valley curent limit to 4.3A. If ı work no load case, MOSFETs switching. But ıf work under the full load, 1A etc. switch node enter nonperiodic switching cycle. To solve this problem, when ı read the datasheet, I found this note: "To prevent forcing current back into the main power supply, potentially boosting the input supply to a dangerous voltage level, forced continuous mode of operation is disabled when the TRACK/SS voltage is below the reference voltage during soft-start or tracking. During these two periods, the PGOOD signal is forced low."

So, If ı work in between the no load and full load then this IC enter the which mode?