For a scala compiler, what are the differences between 'Symbol '***' is missing from the classpath' error and 'object *** is not a member' error?

Question

In a recent experiment, I tried to use maven-shade plugin to move all classes in a package com.original.work under a scala library into a different package, and compile into a new project JAR:

      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-shade-plugin</artifactId>
        <executions>
          <execution>
            <phase>package</phase>
            <goals>
              <goal>shade</goal>
            </goals>

            <configuration>
              <shadeTestJar>true</shadeTestJar>

              <createSourcesJar>true</createSourcesJar>
              <shadeSourcesContent>true</shadeSourcesContent>

              <createDependencyReducedPom>true</createDependencyReducedPom>
              <dependencyReducedPomLocation>
                ${project.build.directory}/dependency-reduced-pom.xml
              </dependencyReducedPomLocation>
              <!--              <generateUniqueDependencyReducedPom>true</generateUniqueDependencyReducedPom>-->

              <!--              <keepDependenciesWithProvidedScope>true</keepDependenciesWithProvidedScope>-->
              <promoteTransitiveDependencies>true</promoteTransitiveDependencies>

              <!--              <shadedClassifierName>${spark.classifier}</shadedClassifierName>-->
<!--              <useBaseVersion>true</useBaseVersion>-->

              <relocations>
                <relocation>
                  <pattern>com.original.work</pattern>
                  <shadedPattern>com.relocated.work</shadedPattern>
                </relocation>
              </relocations>

              <artifactSet>
                <includes>
                  <include>com.original.work:work</include>
                </includes>
              </artifactSet>
            </configuration>
          </execution>
        </executions>
      </plugin>

Unfortunately, this JAR behave strangely if being used by other scala projects. E.g. if the project 'work' already has a trait defined under a package:

package com.original.work.utils

trait IDMixin {

...

Then for any other scala project that use the new JAR, using IDMixin will fail. Specifically:

• If I import com.original.work.utils.IDMixin directly, I will get the following exception:

[ERROR] .../ExampleOld.scala:4: object original is not a member of package com
[ERROR] object ExampleOld extends com.original.work.utils.IDMixin{}
[ERROR]                               ^

• If I import com.relocated.work.utils.IDMixin, I will get the following exception:

[ERROR] .../Example.scala:3: Symbol 'term com.original.work.utils' is missing from the classpath.
This symbol is required by ' <none>'.
Make sure that term utils is in your classpath and check for conflicting dependencies with `-Ylog-classpath`.
A full rebuild may help if 'IDMixin.class' was compiled against an incompatible version of com.original.work.

So my questions are:

1. What are the differences between these 2 error information?

2. If this problem is caused by maven-shade plugin, what should I do to fix it? If not possible, are there any other build tools (sbt, gradle, mill) capable of completing the relocation job?

Thanks a lot for your opinion