Further examination of the chart shows that a VSWR of 2.6:1 results in only about 1 dB of transmission loss.
A high VSWR of 6:1 shows just a 3 dB transmission loss, but this is 1/2 an S-unit.
You will still be getting out but this is becoming a significant loss.
Your feedline will be dissipating more power than it should, and there may be other serious things wrong with your antenna system.