As a long time forum member and experienced DP-32 user, and as this problem just cropped up, it could be a firmware issue; or a user setting/parameter error; and less likely a hardware issue.
I suggest you start troubleshooting by making sure you have the latest firmware.
Then load your factory settings template, create a new test song from scratch using "song001"; record and play back some test tracks; and apply effects one at a time, turning each on then off sequentially for each Input and Track.
There's also a detailed "Signal Troubleshooting" post in the sticky thread "Equipment Related Tips" pinned in the blue area on the first page of this "2488-DP and 24/32/SD Digital Porta Studios" forum. There's an index in the first post of that sticky.
If the problem also presents in your test, then a call or email to TASCAM support may be your best option for identifying and resolving the problem.
If the problem doesn't present in your test, and the "Signal Troubleshooting" post didn't resolve the issue, then come back to this thread with specific settings, etc. for each Input and Track of the actual song in which the issue presents.
The more detail you can provide, the more likely we'll be able to make informed guesses/suggestions on what the cause(s) may be and corrective steps to take.