PLT cache doesn't appear to be updating

[edwinthinks]

I've had an issue were the PLT seemed to be cached and restored but never seemed to be up to date regardless of changing nothing.

Regardless of nothing changing this would occurs in the build pipeline (which added about a minute in my builds)

mix do compile, dialyzer --plt
--
  | Compiling 24 files (.ex)
  | warning: variable "type" is unused (if the variable is not meant to be used, prefix it with an underscore)
  | lib/you_must_goto/authentications/error_handler.ex:9
  |  
  | warning: unused import Plug.Conn
  | lib/you_must_goto/authentications/error_handler.ex:4
  |  
  | Generated you_must_goto app
  | Finding suitable PLTs
  | Checking PLT...
  | [:asn1, :base64url, :certifi, :compiler, :connection, :cowboy, :cowlib, :crypto, :db_connection, :decimal, :ecto, :ecto_sql, :eex, :elixir, :envy, :file_system, :gettext, :guardian, :hackney, :idna, :jason, :jose, :kernel, :logger, :metrics, :mime, :mimerl, :oauth2, :phoenix, :phoenix_ecto, :phoenix_html, :phoenix_live_reload, :phoenix_pubsub, :plug, :plug_cowboy, :plug_crypto, :postgrex, :public_key, :ranch, :runtime_tools, :ssl, :ssl_verify_fun, :stdlib, :telemetry, :ueberauth, :ueberauth_google, :unicode_util_compat]
  | Looking up modules in dialyzer.plt
  | Finding applications for dialyzer.plt
  | Finding modules for dialyzer.plt
  | Removing 19 modules from dialyzer.plt
  | Checking 1100 modules in dialyzer.plt
  | Adding 217 modules to dialyzer.plt
  | No :ignore_warnings opt specified in mix.exs and default does not exist.
  |  
  | exit code: 0 duration: 66s

Only by cache clearing manually via semaphore ci, and rebuilding the plt from scratch was I able to get my build speeds less than a minute.

Wonder if anyone else is having this issue.