Make sure you aren't getting the warning due to too much allocated RAM. Even if you are close to the limit but not breaking it, RAM allocation might still be the cause of the crash. Try allocating 100-250MB less than the maximum, depending on your device. Keep in mind that when using big modpacks, you might also be crashing because you don't have enough allocated memory (that's if you see java.lang.OutOfMemoryError in your log file).
Highest RAM allocation doesn't mean highest performance. Your might usually gain tens of FPS by figuring out which RAM allocation setting runs Pojav the best on your device.