Sold Business Assets Through an Online Marketplace

I have an audio production business, and sold a bunch of older production gear, both Section 179 and Deminimus Safe Harbor, through an online marketplace (Reverb.com). Previously, I simply reported these sales of gear on Form 4797, which shows up on my 1040 - and is not subject to self-employment tax.

However, since I'll be getting a 1099-K this year from the marketplace for these business asset sales, Turbo Tax is placing that income directly into my Schedule C, which will make it subject to SE Tax. Plus, if I still enter it on the 4797, as I'm supposed to, much of that gain will show up on both my Schedule C AND my 1040. I can't be the only small business having this dilemma, but there is zero info on the net. Any advice would be appreciated.