Eclipse autocompletion (Ctrl+Space) within message shows only "group" after "required"

[EisW]

Protocol Buffer Editor 2.3.2.20160916184 on eclipse oxygen.2
("Eclipse for Parallel Application Developers", 4.7.2.20171218-0600)

When writing a proto file within a message defintion the autocompleteion feature after input of keyword (required or optional or repeated) does only show "group" as input helper. In case of repeated the keyword "group" and "oneof" are presented, but types still missing.

Syntax highlighting works fine, only autocompletion fails.

The error seems independend from "syntax = "proto2";" in first line of proto file.

Besides: On start of line there are all types (like uint32)

Here the types are shown::

// here seems okay
message test {
    <here all possible types are shown with <ctrl+space>>
}

here not - Error::

// error
message test {
    require <here only "group" is shown in autocomplete list after <ctrl+space>>
}

Previously we used 1.4.1, which was working okay.