Also, do not set constraint if both TR and duration are numbers

src/sequences.jl

@@ -28,7 +28,7 @@ struct Sequence <: ContainerBlock
             to_block.(blocks),
             get_free_variable(TR),
         )
-        if !(TR isa Number && isinf(TR))
+        if !(TR isa Number && (isinf(TR) || duration(seq) isa Number))
             @constraint global_model() seq.TR >= duration(seq)
         end
         return seq