• by Gavin O'Malley  @mp_gavin, May 22, 2015

Tired of defending one bad management decision after another, early Twitter investor Chris Sacco is vowing to take the company to task.

“I never expressed any frustration or disappointment at missed opportunities or any exasperation at what wasn’t happening,” Sacco explains in a new blog post. “However, a recent Periscope I did with Jim Cramer at CNBC changed my stance on that.”

According to Sacco, he and Cramer -- a longtime critic of current Twitter CEO Dick Costolo -- shared “insights as to what we each thought was going wrong and what could be better.”

“Those messages resonated with [Periscope] viewers, some of whom were Twitter employees,” according to Sacco -- who professes to owning “a lot of Twitter stock.”

As a result, Sacco says he is preparing to post “a few things that I personally hope the Twitter team will accomplish.”

The critique couldn’t come at a worse time for Twitter, which is still trying to explain its poor first-quarter earnings.

In late April, Costolo blamed the weak quarter on “lower-than-expected contribution from some of our newer direct-response products.” Worse yet, he said the company expected the problems to persist for the remainder of the fiscal year.

Revenue for the first quarter was $436 million, which -- while up 74% year-over-year -- was lower than analysts’ estimates of about $457 million.

Among other unyielding problems, Twitter remains a hotbed for bullying and abusive trolls.

Echoing earlier comments by Costolo, Vijaya Gadde, general counsel for Twitter, recently wrote in The Washington Post: “Even when we have recognized that harassment is taking place, our response times have been inexcusably slow and the substance of our responses too meager.”

Costolo has faced increasing pressure to relinquish his role as Twitter’s CEO. While key company insiders have reportedly come to his defense, Sacco’s about-face could represent a turning of the tide.

Analysts, meanwhile, are holding their tongues until Sacco lays out his specific assessments.

Sacco “just said ‘I've always been a fan, but now I'll start to criticize them more,’” notes Forrester analyst Nate Elliot. “But he doesn't actually criticize them.”

Twitter didn’t respond to request for comment by press time.