Until the 10th of May the Erlang/OTP 24.3.4.17 patch had an incorrect prebuilt archive on github (the otp_src_24.3.4.17.tar.gz artifact), which meant that if used it would install OTP 24.3.4.15 and not the intended patch.
Tools such as kerl and by extension asdf use the prebuilt archive, so if you used those to install 24.3.4.17 you will need to rebuild your system to get the correct Erlang version. In order to get the proper version in kerl you need to do kerl cleanup 24.3.4.17 and then re-install it.
The official docker images are unaffected as they build from the git tag.
The fault was due to human error on my behalf and was reported by the Cloudant Team here.