Drawing relations between tokens causes error

[reckart]

In a fresh project, when I draw relations between tokens, then I get

2021-04-11 19:14:00 ERROR [admin] CasDoctor - [DanglingRelationsCheck] Relation [de.tudarmstadt.ukp.dkpro.core.api.syntax.type.dependency.Dependency] with id [68854] has loose ends.
Relation [de.tudarmstadt.ukp.dkpro.core.api.syntax.type.dependency.Dependency] attached to feature [pos].
Source: null
Target: null
2021-04-11 19:14:00 ERROR [admin] CasDoctor - [DanglingRelationsCheck] Relation [de.tudarmstadt.ukp.dkpro.core.api.syntax.type.dependency.Dependency] with id [68862] has loose ends.
Relation [de.tudarmstadt.ukp.dkpro.core.api.syntax.type.dependency.Dependency] attached to feature [pos].
Source: null
Target: null
2021-04-11 19:14:00 WARN [admin] RelationRenderer - Relation [de.tudarmstadt.ukp.dkpro.core.api.syntax.type.dependency.Dependency] with id [68854] has loose ends - cannot render.
2021-04-11 19:14:00 WARN [admin] RelationRenderer - Relation [de.tudarmstadt.ukp.dkpro.core.api.syntax.type.dependency.Dependency] with id [68862] has loose ends - cannot render.
2021-04-11 19:14:00 WARN [admin] ApplicationPageBase - admin: Relation [de.tudarmstadt.ukp.dkpro.core.api.syntax.type.dependency.Dependency] with id [68854] has loose ends - cannot render.
Relation [de.tudarmstadt.ukp.dkpro.core.api.syntax.type.dependency.Dependency] attached to feature [pos].
Dependent: null
Governor: null
2021-04-11 19:14:00 WARN [admin] ApplicationPageBase - admin: Relation [de.tudarmstadt.ukp.dkpro.core.api.syntax.type.dependency.Dependency] with id [68854] has loose ends - cannot render.
Relation [de.tudarmstadt.ukp.dkpro.core.api.syntax.type.dependency.Dependency] attached to feature [pos].
Dependent: null
Governor: null
2021-04-11 19:14:00 WARN [admin] ApplicationPageBase - admin: Relation [de.tudarmstadt.ukp.dkpro.core.api.syntax.type.dependency.Dependency] with id [68854] has loose ends - cannot render.
Relation [de.tudarmstadt.ukp.dkpro.core.api.syntax.type.dependency.Dependency] attached to feature [pos].
Dependent: null
Governor: null
2021-04-11 19:14:00 WARN [admin] ApplicationPageBase - admin: Relation [de.tudarmstadt.ukp.dkpro.core.api.syntax.type.dependency.Dependency] with id [68862] has loose ends - cannot render.
Relation [de.tudarmstadt.ukp.dkpro.core.api.syntax.type.dependency.Dependency] attached to feature [pos].
Dependent: null
Governor: null
2021-04-11 19:14:00 WARN [admin] ApplicationPageBase - admin: Relation [de.tudarmstadt.ukp.dkpro.core.api.syntax.type.dependency.Dependency] with id [68854] has loose ends - cannot render.
Relation [de.tudarmstadt.ukp.dkpro.core.api.syntax.type.dependency.Dependency] attached to feature [pos].
Dependent: null
Governor: null
2021-04-11 19:14:00 WARN [admin] ApplicationPageBase - admin: Relation [de.tudarmstadt.ukp.dkpro.core.api.syntax.type.dependency.Dependency] with id [68862] has loose ends - cannot render.
Relation [de.tudarmstadt.ukp.dkpro.core.api.syntax.type.dependency.Dependency] attached to feature [pos].
Dependent: null
Governor: null
2021-04-11 19:14:00 ERROR [admin] ApplicationPageBase - admin: Error: IllegalPlacementException: Cannot create another annotation of layer [Dependency] at this location - stacking is not allowed for this layer.: Cannot create another annotation of layer [Dependency] at this location - stacking is not allowed for this layer.

Originally posted by @jcklie in https://github.com/inception-project/inception/issues/2141#issuecomment-817340648