Troubleshooting toslink input problems on DACs

I have two systems set up in my house, both utilize the Airport Express optical out to a DAC. Both started having playback issues at the same time, one system cuts out ever 5-10 seconds and the other sounds distorted or fuzzy every few seconds. Both DACs play fine when using USB straight from the computer, both AE play fine using the regular stereo out. Anyone have similar issues? Could it be a network problem, maybe a cable problem? I did purchase a new AE and tried it on both DACs and still had the same playback issues.
I have found that the Optical connection is very non reliable at keeping a good connection between a transport and a Dac. Sounds like your are having a similar issue.I would switch to something that would allow you to use a Unbalanced or Balanced cable.I use a RCA cable to a DIP (digital processor) then XLR cable OUT to a DAC, then out using analogue RCA to pre amp. With my setup the sound is like a warm turntable very analogue sounding and easy to listen to for extended periods. I use a McIntosh cd player as a transport and I run digital RCA to a Monarchy Audio DIP then out to a MSB Nelson DAC. The signal is ROCK solid. When I was using a Sony player with Optical it was not as good.
What cables are you using?

Since using DH Labs cables I have had no problems with optical - they lock in place and are one of the fastest cables out there

My surround sound system sounded so much better once I put them In the loop.

Had them on my iMac/DAC for streaming and no problems

They sound amazing as well - they beat Chord and Van den Hul optical cables by a long way
troubleshooting ideas. as you have it narrowed down to the toslink you can swap in a new cheap cable to eliminate that as a possibility. you can swap your cable end for end and that may alter the behavior if the fiber end treatment is shot. try another toslink source like a tv of video game console and test the source. if none of those alter the problem you likely have a messed up dac.