TuneSpan hanging up on spanning after OS Sierra upgrade

After upgrading to MacOS Sierra, TuneSpan hangs up when attempting to span files. This is the case in both normal and crash recovery mode. For some reason, I can restore files from the remote drive to my hard drive just fine - it's only the spanning from the HD to the remote drive that is affected. The remote drive is a Synology DS216play, which has worked well with TuneSpan for many months up to right around the time of the OS upgrade.

The hang-up requires a force quit of the application, which prompts TuneSpan to reopen in crash recovery mode. I've tried exiting out of crash recovery mode and starting fresh, trying to follow through the steps in crash recovery mode, restarted the computer several times and tried each mode after restarting several times, and rebooting the Synology. Any recommendations for anything else to try? I've (hopefully) attached a screenshot demonstrating the problem - note the "elapsed time" at the bottom. I love this application and have been using it for years without a problem until now, so I hope there's a solution out there. Thanks for your help.