If thats the case it does sound like the SSD is failing. This series uses a custom mSATA blade drive.
You’ll need to replace it, your options are limited either going with another Apple driver or [product|IF188-121|OWC Aura Pro SSD] and you might want to get a larger drive if you find your drive is more than 3/4 full. The reason here is you want to leave a partition of the drive unused so the OS and your apps have some elbow room for Virtual RAM, caching and scratch space use.
Reference: [https://beetstech.com/blog/apple-proprietary-ssd-ultimate-guide-to-specs-and-upgrades#hdr-7|The Ultimate Guide to Apple’s Proprietary SSDs]