hi. i have the same issue . my 0,2 btc worth dgb didn't arrive from poloniex to my bittrex wallet for more than 12 hours.. tx id is not on block explorer. at fist i thought it was a clogging issue but ten minutes ago i sent 1000 dgb from crytopia to bittrex and it arrvived. so this doesnt look like a clogging issue.
Poloniex does this a lot with various coins. They create txs and don't broadcast them. File a support ticket fast because their respone time to fix it will be one to two months if you are lucky.
DGB never gets clogged. It is the fastest UTXO blockchain in the world and has new blocks every 15 seconds. DGB can handle as many txs as people can throw at it. Never blame the DGB blockchain of having a clogging issue. TXS clear very fast and confirm fully within minutes, not hours like other coins.