SCOPUS has discontinued from 2018 onward meaning that you have published any article with this journal by Dec 2017, you can refer to that as SCOPUS indexed article but after Jan 2018, you can not say so anymore.
I found that the Reason for discontinuation is "Publication Concerns". what does this mean? it is related to open acess journals aren't accepted in scopus?
I am afraid that there is no language correction in IJAER papers. I found some papers from Indonesia has been published although some Indonesian words are still there. This could be one reason why the Journal is now excluded by Scopus.
No. I checked earlier in the week and they are not indexed. This journal send invitation to authors and any journal that does that is usually not indexed in major indexing databases
I think, removal from the database is governed by Scopus to keep the minimum requirement for a standard reputable journals. It is very normal to get back to the data base once reviewing results of manuscripts are improved.