What is your configured write block size for the namespace. The maximum allowed record size is <= write block size. You can check it out in namespace section in /etc/aerospike/aerospike.conf file. If the write block size is configured < 200k then you will see symptoms as observed and increasing it should work.
Please make sure to read the README at the top of the documentation of the GitHub repo for a problem that may occur with storing binary data in strings. Specifically if your binary data may include a null byte (\0) in the middle of the string. There’s a workaround described there.