I never received a reply, of course. I've sort of come to expect that when reporting issues with free Google resources. So, in the mean time I clicked on the link for the Google Finance Blog to see if anybody else had reported the problem.
Oh, oh. Here is the top post, dated two years ago:
Thursday, August 9, 2012 at 9:20 AMPosted by Karolina Netolicka, Product Manager
Thanks to everyone who has been a loyal reader of the blog over the last five years. After some consideration, we've realized that we're just not generating enough content here to warrant your time, so we won't be posting here any longer.
Instead, we'll start contributing to the Inside Search blog, so tune in there for updates on Google Finance.
Looking through the referenced Inside Search Blog blog turned up no discussion on the broken Google Finance portfolio tracker, but a more general search turned up plenty of discussions on the topic, such as this one. Bottom line: Google Finance is broken, and unsupported.
More recently, about three weeks ago I went over to the Google Finance Stock Screener using, as always, Google's Chrome Browser on my Linux box, and I found it to broken as well, and fairly recently. I had used it just one month prior.
Digging a little deeper, I realized that their stock screener page itself wasn't really broken; it worked fine when using Firefox. However, the page was not being rendered properly by the Google Chrome browser; elements of the page overlapped each other, making the page unusable.
Here's how the screener page is supposed to look (Firefox):
And here's how it looks in Chrome:
The slider elements overlay the the numeric input boxes on the right making it impossible to set screener selection criteria.
Bottom line: it is probably not a good idea to include Google products in any mission-critical applications, because you simply never know if they will continue to be supported in the future.