Newly separated HP Inc. (HPQ) and Hewlett Packard Enterprise (HPE) reported a messy final quarter together on Tuesday, but amid the mishmash, one growing risk jumped out to investors.

For the entire already-split enterprise, HP reported slightly less revenue than Wall Street expected at $25.7 billion, a 9% drop marking the 16th out of the past 17 quarters when sales declined. And adjusted earnings per share of 93 cents were below Wall Street's 97 cents expectations. There was also some minor tweaking of guidance for the next year on both sides.

But shares of HP Inc., the PC and printer arm, have tanked on Wednesday, dropping 14% to $12.61 in midday trading.

And that's not about a few tweaks, the messy alterations to the timing of job slashing and cost cutting or even the general weakness in PC and printer markets. Rather, HP let slip that there's a problem with its cash machine, responsible for over 90% of its operating income: ink. Printers and PCs are a low- to no-margin business. It's the supplies that provide almost all the profits for HP.

That's why analysts and investors must have sat up straight in their Aeron chairs when they heard new HP Inc. CEO Dion Weisler explain that the weak dollar coupled with a growing price war from Asian suppliers is leading consumers to buy higher-end printers once favored by corporate shoppers. In the past, investors have been able to model HP's profits fairly easily by looking at past printer sales and extrapolating how much ink would be ordered in the future. But because consumers use a lot less ink than companies, HP isn't getting the same bump in ink sales it previously did from sales of those high-end models.

"The unintended result is that we are not getting the yield per unit we would have expected on some of these units," Weisler said on a call with analysts. "We see this impacting our supplies revenue trajectory. Q4 ‘15 supplies revenue was not where we expected to be and we have more work to do. We will accelerate initiatives across all the levers we pull to improve the supplies revenue trajectory."

The "revenue trajectory" is Wall Street-speak for results in upcoming quarters. It seems HP has a big problem that will continue and the solution may not yet be in sight.

On the Enterprise side, run by CEO Meg Whitman, there wasn't much in the way of significant news. Following news that HP was abandoning its efforts to sell its own cloud services platform, Whitman announced that her company would partner with Microsoft's (MSFT) Azure cloud as part of a strategy to sell corporate customers on comprehensive "solutions" to their IT needs.

That pleased investors, as shares of Whitman's unit rose 3% to $14.07 in midday trading. Whether that will be enough to revive the enterprise unit's fortunes over the long haul remains to be seen.