Also have the same problem with Restrap front harness…so much so it has tyre rub marks. Run a front rack these days though (and barely need to use it anyway) but I could see voile straps making a lot of sense.
I used the voile straps with foam spacers to run my bigxtop bag on a rack without the clickfix fastening. Works a treat.
Edit: they were very good about replacing a dry bag that ripped.
If you're getting new straps then you might be sorted, but depending on both whether that is 25mm webbing (probably) and your handiness with a sewing machine, I have used this style of buckle on a few bags and never had any slipping issues:
Also have the same problem with Restrap front harness…so much so it has tyre rub marks. Run a front rack these days though (and barely need to use it anyway) but I could see voile straps making a lot of sense.
I used the voile straps with foam spacers to run my bigxtop bag on a rack without the clickfix fastening. Works a treat.
Edit: they were very good about replacing a dry bag that ripped.