Camel Ruby integration fails with parallel processing

When a Camel route contains a Ruby invocation, of this form:

.to("language:ruby:puts $request.body;result = $request.body")

and this route is invoked in parallel from a SEDA parallel consumer:

from("seda:parallel?concurrentConsumers=5")

then the route fails intermittently with the following exception message:

NoMethodError: undefined method `body' for nil:NilClass
(root) at <script>:1

The same route works correctly with Camel 2.8.0. In addition, execution of the route is 2-3 times slower with Camel 2.12.0 than it was with 2.8.0; it is not clear whether this reduction in throughput is associated with the errors or not.