While groupId:artifactId:version is the most common way of defining co-ordinates for 99% of usecases, there are occasionally more complex co-ordinates that involve specifying the packaging and classifier.
The full set of valid co-ordinate patterns can be seen here for bazel, the problem is that renovate only comprehends the 3-arity form, and [speculating] either doesn't support 4,5-arity, or there is a bug in 4,5-arity.
Spec: https://github.com/bazelbuild/rules_jvm_external/blob/master/specs.bzl#L132
Using this particular maven artifact as a great example of 5-arity: https://repo1.maven.org/maven2/io/netty/netty-transport-native-epoll/4.1.113.Final/
It is necessary to specify the packaging as jar and the classifier linux-x86_64 as part of the co-ordinates so
"io.netty:netty-transport-native-epoll:jar:linux-x86_64:4.1.87.Final (5-arity) is valid in a maven_install file.
when renovate raises a PR for a 5-arity entry, it incorrectly offers io.netty:netty-transport-native-epoll:4.1.113.Final:linux-x86_64:4.1.87.Final as the upgrade replacing the third element (jar) with the new version.
when renovate raises a PR for a 5-arity entry, it should offer io.netty:netty-transport-native-epoll:jar:linux-x86_64:4.1.113.Final with the last element in the array being upgraded.