In BW 5.14.0 when using HTTPS and PCM is required then the property bw.plugin.http.client.usePersistentConnectionManagerForSSL=true must be set.
It is not sufficient to use the property bw.plugin.http.client.usePersistentConnectionManager=true.

If using HTTPS and setting bw.plugin.http.client.usePersistentConnectionManager=true but not setting bw.plugin.http.client.usePersistentConnectionManagerForSSL=true then you will run into various SSL errors depending on the configuration of SSL. 
An example of such an error is
" fatal, description = certificate_unknown  " inside the section " *** Certificate chain " of SSL debug logs.

If using HTTPS and setting bw.plugin.http.client.usePersistentConnectionManager=true and also setting bw.plugin.http.client.usePersistentConnectionManagerForSSL=true then you won't see the same SSL errors as above.