The only fundamental change is overall market sentiment. PRR was...

The only fundamental change is overall market sentiment. PRR was a safe haven when the market was falling, it stood up whilst many other stocks were going south. Now that the market has picked up, there are other more attractive short term options. Regardless whether the economy starts going gangbusters, a company in R&D are not likely to reap the rewards like a company with sales relying on and benefiting from a buoyant economy.
Unless there is volatility in the share price or you have a long term outlook and patience to boot, it is dead money in the very short term, from a traders point of view. I will always hold some stock but l will not tie up too much equity whilst the market recovers and beaten down stocks start to rebound. It is true, fundamentally the company itself is still on track and remains a very bright prospect.