Registering a new user in 3.0.2

Hello @kaitlin, @smecher, @geekm1983, @Vladislav_Mavrin, @NateWr,

I have encountered an apparently similar issue.
I am running OJS 3.0.2, with Bootstrap3 “journal” theme (v.1.0.2, which should be compatible), and users are unable to register.
When filling the “register” form and confirming registration, the “register” page loads again, with fields left blank. No email confirmation is sent to user, and user is not created in system. I have been able to replicate the issue locally, and the only error line I got in the log (this is the “non-verbose” log I can access on my shared hosting platform) is:
[Tue Sep 05 11:33:03.983167 2017] [ssl:error] [pid 16834:tid 7] AH02032: Hostname HELLO provided via SNI and hostname clararevue.ulb.be provided via HTTP have no compatible SSL setup

A similar issue was also posted by @geekm1983 in another post here: https://forum.pkp.sfu.ca/t/users-cant-register/32627
All solutions tend to stress the use of an incompatible version of Bootstrap3. However, I am running Boostrap3 v.1.0.2, which should be compatible with OJS.3.0.2.
Also, I have checked that Users have the possibility of self-registrating to the journal for certain roles (author, reader, reviewer) as suggested by @asmecher and @NateWr in this post here: https://forum.pkp.sfu.ca/t/users-can-not-register/19209
Finally, since I have the Orcid plugin installed which is also giving problems, as I did mention in this post here: ORCID iD not retrieved - #23 by afisher, I have disabled the Orcid plugin, to make sure there is no interference (actually, my sense is that solving this issue will solve my Orcid plugin problem…).
Nothing will do.
Any suggestion?
Would it make sense to install again the Bootstrap3 v.1.0.2 from here https://github.com/NateWr/bootstrap3/tree/ojs-3.0.2? Is there any risk that crushing my existing Bootstrap3 files will cancel some personalized settings?

Thank you for you prompt answer and support.