Fundamentals are looking good IMO albeit the recent flash crash. The scaling issue that seemed to bother people a lot in 2015-2017 has been addressed
in the mean time thanks to SegWit being deployed. Sidechains are rolling out, though I don't really know how that'll help but they're there and people are expecting them to somewhat alleviate the load in the main chain.
Well, there was
a pretty serious bug in the last several releases of the
reference implementation (run by most of the network) that was fixed a couple months ago. It could have been used to inflate the Bitcoin supply:
This weeks major bitcoin bug was even worse than developers initially let on.
The bug originally rocked the bitcoin world when it was reported the vulnerability could be used to shut down a chunk of the network.
While this sounded bad enough for many, it turns out developers for Bitcoin Core kept a second, bigger part of the bug a secret. As disclosed through an official Common Vulnerabilities and Exposures (CVE) report, an attacker could have actually used it to create new bitcoin above the 21 million hard-cap of coin creation thereby inflating the supply and devaluing current bitcoins.
A similar bug/exploit happened back in 2013 or 2014 I believe that flooded the market with fake bitcoins. Luckily it was immediately fixed and nothing severe has happened in the market.