TLA+ Toolbox unexpected exception - tla+

Question

I'm studying TLA+, and am running the lecture example code
EXTENDS Integers
VARIABLES i, pc
Init == (pc = "start") /\ (i = 0)
Pick == /\ pc = "start"
/\ i' \in 0..1000
/\ pc' = "middle"
Add1 == /\ pc = "middle"
/\ i' = i + 1
/\ pc' = "done"
Next == Pick \/ Add1
but I'm running into unexpected exception errors like
unsuccessfully trying to load custom FPSet class: tlc2.tool.fp.OffHeapDiskFPSet
TLC threw an unexpected exception.
This was probably caused by an error in the spec or model.
See the User Output or TLC Console for clues to what happened.
The exception was a java.util.concurrent.ExecutionException
: java.lang.NullPointerException
And User Output:
java.lang.reflect.InvocationTargetException
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.base/java.lang.reflect.Constructor.newInstance(Unknown Source)
at tlc2.tool.fp.FPSetFactory.loadImplementation(FPSetFactory.java:206)
at tlc2.tool.fp.FPSetFactory.getFPSet(FPSetFactory.java:109)
at tlc2.tool.fp.MultiFPSet.getNestedFPSets(MultiFPSet.java:68)
at tlc2.tool.fp.MultiFPSet.<init>(MultiFPSet.java:61)
at tlc2.tool.fp.FPSetFactory.getFPSet(FPSetFactory.java:105)
at tlc2.tool.fp.FPSetFactory$1.call(FPSetFactory.java:136)
at tlc2.tool.fp.FPSetFactory$1.call(FPSetFactory.java:1)
at java.base/java.util.concurrent.FutureTask.run(Unknown Source)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.base/java.lang.Thread.run(Unknown Source)
Caused by: java.lang.OutOfMemoryError
at java.base/jdk.internal.misc.Unsafe.allocateMemory(Unknown Source)
at jdk.unsupported/sun.misc.Unsafe.allocateMemory(Unknown Source)
at tlc2.tool.fp.LongArray.<init>(LongArray.java:79)
at tlc2.tool.fp.OffHeapDiskFPSet.<init>(OffHeapDiskFPSet.java:138)
java.lang.reflect.InvocationTargetException
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.base/java.lang.reflect.Constructor.newInstance(Unknown Source)
at tlc2.tool.fp.FPSetFactory.loadImplementation(FPSetFactory.java:206)
at tlc2.tool.fp.FPSetFactory.getFPSet(FPSetFactory.java:109)
at tlc2.tool.fp.MultiFPSet.getNestedFPSets(MultiFPSet.java:68)
at tlc2.tool.fp.MultiFPSet.<init>(MultiFPSet.java:61)
at tlc2.tool.fp.FPSetFactory.getFPSet(FPSetFactory.java:105)
at tlc2.tool.fp.FPSetFactory$1.call(FPSetFactory.java:136)
at tlc2.tool.fp.FPSetFactory$1.call(FPSetFactory.java:1)
at java.base/java.util.concurrent.FutureTask.run(Unknown Source)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.base/java.lang.Thread.run(Unknown Source)
Caused by: java.lang.OutOfMemoryError
at java.base/jdk.internal.misc.Unsafe.allocateMemory(Unknown Source)
at jdk.unsupported/sun.misc.Unsafe.allocateMemory(Unknown Source)
at tlc2.tool.fp.LongArray.<init>(LongArray.java:79)
at tlc2.tool.fp.OffHeapDiskFPSet.<init>(OffHeapDiskFPSet.java:138)
... 15 more
Does anyone know how to fix this?
update:
TLA+ toolbox version:
This is Version 1.6.0 of 10 July 2019 and includes:
- SANY Version 2.1 of 23 July 2017
- TLC Version 2.14 of 10 July 2019
- PlusCal Version 1.9 of 10 July 2019
- TLATeX Version 1.0 of 20 September 2017

Answer 1

does your specification file begins with a module line?
That is:
------------------------------- MODULE MySpec -------------------------------
if the file is MySpec.tla.
With this I could perform model-checking <>(pc = "done") using TLC both in the TLA+ toolbox version 1.6.1 and with TLC 2.14 from tla2tools.jar (command line). Nb: it fails due to stuttering.