Dealing with Underperforming Co-Founder

I'm a co-founder at a young (1-2 years old) startup. We established an equal equity structure to indicate each co-founder would contribute equally to the company's growth. However, it has become apparent that this is not the case.

My co-founder (PC) is not technical. Our startup makes software and hardware, and PC does not have the knowledge to be involved in either. Over time, many non-technical tasks have fallen into my lap because PC has consistently missed deadlines and meetings, delivered sub-par work product (e.g. writing riddled with spelling and grammatical mistakes, misrepresentation of our product to potential investors, spreadsheets with completely incorrect calculations), and hasn't taken the initiative to learn on the job like me or my other co-founder (OC).

OC and I have had many conversations with PC about this, and we've been met with an acknowledgment and a promise to do better, but things rapidly devolve again. I've completely lost trust in PC, and ordinarily I feel this would not have been tolerated at other companies.

Problem is: OC and I are pretty much operating at 100%, and PC does do work. It's usually not great, and the output per time/money spent is low, but it's work. OC and I aren't certain we have the bandwidth to pick up PC's work; if we broach the topic of equity redistribution, we're afraid PC will demand equal equity or they leave the company, effectively taking the company hostage. We're also entering a funding round and we're scared to set off alarms.

After reading through HN posts, I have to say now doesn't seem like the time to act on equity redistribution or firing. But when IS the time? PC isn't pulling their weight, they're a drain on company resources, they've been given so many chances without improvement, but we do need somebody to manage a bit of work OC and I may not be able to handle ourselves.

Do we just have to let PC freeload on OC's and my work? Do we wait until the company can feasibly replace PC?