We've been doing some digging in this department for a bit now, and can't find any sort of notable news that would send the stock price down as much as it is.
The only notable news as of late was TC Energy's all stock acquisition of TC Pipelines, a company it had a large interest in previously. The acquisition was for around $1.7 billion dollars and is now being investigated by a couple law firms, which cite that TC Pipeline's board of directors agreed to an inadequate merger agreement.
Considering the company (TC Pipelines, ticker TCP) has a market cap of around $2.08 billion at the time of me writing this and the deal is for $1.7 billion, this is far below current market value and significantly below pre-pandemic values. So, there may be merit there.
However, I don't see this impacting TC Energy's stock price. A lot of pipelines and oil producers have taken a tumble in December. Fundamentally, nothing has changed.