Not really a wrong answer here. Math says invest immediately, but you're only talking about waiting 2 months for 3-4% of your 'stache.
Personally, we just did a cash-out refinance on the house. I immediately funded the 2019 soloK and our IRAs, but I'm waiting until January for further investments and then I'll make the big deposit for 2020 soloK and IRAs. We've been getting closer to the funding deadlines for these accounts than I'd like for a lot of reasons the last couple of years, so this move will buy me a few years of being "caught up" in that regard - even if we fall behind again on the contributions, it will take a while to eat up all the extra time we bought with this transaction. Basically, making a move that is slightly sub-optimal financially in order to save some of my sanity.