This is an extremely low end budget SSD so you cannot expect great performance from it especially once the write cache is filled. From this review, the write performance of this SSD drops to 100MB/s once the write cache is filled:
https://www.tomshardware.com/reviews/kingston-uv400-ssd-review,4730.html
Your SSD has 15 Reallocated Blocks. Most likely before those blocks were reallocated the SSD suffered from even more slowness while the SSD tried to read the bad blocks where the SSD was able to correct the inaccuracies in the data up to a point where there were about 2,000 uncorrectable errors. Uncorrectable errors mean some data corruption has occurred which can happen if a bad block is not reallocated promptly. The health report also shows 64K "resets between command acceptance and command completion" which is definitely going to cause performance issues.
While DriveDx is reporting the SSD as "Failing" for attribute# 187 "Flash Read Fail Count", I don't believe this is a true failure and the high value of this attribute was likely due to the SSD not reallocating the 15 bad blocks in a timely manner. Only continued monitoring of this value will and the reallocated block count will be able to determine if this is a problem (I've seen it happen before if the SSD gets stuck reallocating bad blocks).
The SSD also has reported a temperature of 96C at some point which is way above the maximum temperature of 70C. Once the SSD's temperature reaches 70C the speed of the SSD is throttled in order to help lower the temperature of the SSD. Personally I've never seen an SSD report a temperature of 96C before although I have seen some low end budget SSDs go over the 70C maximum temperature. Usually these low end SSDs end up overheating when writing large amounts of data over a short period of time such as an OS install, or migrating/restoring from a backup, or a large software download, etc.
At this point is hard to say whether this SSD is actually bad or if it is just operating normally being a low end SSD. Only continued monitoring of the health attributes would allow a better interpretation (along with knowing exactly how the SSD is being used during that period). I think you will need to replace this SSD if for no other reason than the SSD was running at 96C at some point. If you want an inexpensive SSD with decent performance, then I suggest getting a Crucial MX500 SSD as they are the best compromise on price and performance assuming Crucial has not silently changed the hardware specifications in the last couple of years since I bought the last MX500 for our organization. Stay away from the Crucial BX500 SSD as it is also a low end budget economy model that can be as slow as a hard drive and also tends to overheat. Keep in mind the majority of SSDs today are low end budget economy models.
