Impinj (NASDAQ: PI), a provider of radio-frequency-identification products and solutions, reported its third-quarter results after the market closed on Nov. 1. Revenue growth nearly ground to a halt during the quarter, and the bottom line plunged into the red. What's worse, Impinj expects to post a revenue decline during the fourth quarter due to slipping endpoint volumes, and management isn't entirely clear on the underlying cause. Here's what investors need to know about Impinj's third-quarter results and fourth-quarter guidance. Impinj results: The raw numbers Metric Q3 2017 Q3 2016 Change (YOY) Revenue $32.6 million $31.0 million 5.2% Net income attributable to common shareholders ($4.9 million) $0.2 million N/A Non-GAAP EPS ($0.08) $0.10 N/A GAAP = generally accepted accounting principles; EPS = earnings per share. EPS Data source: Impinj. Image source: Impinj. What happened with Impinj this quarter? Revenue growth slowed dramatically compared to the second quarter, when Impinj produced year-over-year growth of 31.2%. The company slashed its full-year outlook in August due to several large customers delaying roll-out expansions. GAAP gross margin was 52.1%, down from 53.3% during the second quarter. Non-GAAP gross margin was 53.7%, down from 54.7%. Adjusted earnings before interest, taxes, depreciation, and amortization (EBITDA) was a loss of $1.5 million, down from a gain of $1.4 million during the second quarter. GAAP operating expenses soared 39.3% despite the sluggish revenue growth. Impinj provided the following guidance for the fourth quarter: Revenue is expected to come in between $28.25 million and $29.75 million, down from $33.7 million in the fourth quarter of 2016. Adjusted EBITDA is expected to be a loss between $3.35 million and $4.85 million, down from a gain of $2.40 million during the fourth quarter of 2016. Non-GAAP EPS is expected to be a loss between $0.16 and $0.24, down from a profit of $0.11 during the fourth quarter of 2016. Impinj expects volumes of endpoint integrated circuits (IC) to decrease slightly during the second half of the year. What management had to say Impinj CEO Chris Diorio believes that adoption of the company's RAIN technology is set to explode: "We also see strong fourth-quarter demand. Our market data, sales volumes and, for me personally, deep discussions with partners and end users reinforce my belief that the second RAIN adoption wave is upon us." However, Diorio isn't sure exactly why volumes are slipping in the second half: "Yet even as we see that second wave driving significant reader and gateway volume growth, we see a few percentage points decline in second-half 2017 endpoint IC unit volumes versus first-half. The reasons aren't completely clear to us, but we do not believe our market share has changed materially." Diorio pointed to a strong pipeline of pilot programs as reason for optimism: "As I said we have got 30 fixed reading pilots ongoing now and more in the pipeline. So we are seeing kind of a broad wave of adoption of that fixed reading hands-free infrastructure that's driving transformative business changes for end users in these multiple verticals." Looking forward It's unclear yet whether Impinj's growth problems in the second half of this year are temporary, or if they signal deeper issues at the company. Growing revenue at a rate in excess of 30% was the norm until the third quarter, and an expected revenue decline in the fourth quarter is not at all what investors want to see from a growth stock. Shares of Impinj have lost nearly two-thirds of their value since peaking in June, a brutal decline. With management not certain about what's causing the decline in sales, it's hard to say when the company will return to growth. 10 stocks we like better than ImpinjWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the 10 best stocks for investors to buy right now... and Impinj wasn't one of them! That's right -- they think these 10 stocks are even better buys. Click here to learn about these picks! *Stock Advisor returns as of October 9, 2017Timothy Green has no position in any of the stocks mentioned. The Motley Fool recommends Impinj. The Motley Fool has a disclosure policy.