My suspicion is that the problem occurs, because the PWM for pin 11 uses timer 2 which is the same timer used by the library
<IRremote.h>.
I'm searching the web, to confirm about the pin 11 PWM,
and there is a conflict, but I haven't found confirmation yet.
RV mineirin
PS:
Timer output Arduino output Chip pin Pin namePin name
OC0A 6 12 PD6 TIMER 0
OC0B 5 11 PD5 TIMER 0
OC1A 9 15 PB1 TIMER 1
OC1B 10 16 PB2 TIMER 1
OC2A 11 17 PB3 TIMER 2
OC2B 3 5 PD3 TIMER 2
https://www.arduino.cc/en/Tutorial/SecretsOfArduinoPWM