Versions:

Linux 4.13.0-38-generic #43~16.04.1-Ubuntu SMP Wed Mar 14 17:48:43 UTC 2018
x86_64 x86_64 x86_64 GNU/Linux

GNU bash, version 4.3.48(1)-release (x86_64-pc-linux-gnu)

lambda2 version: 1.9.4
SeqAn version: 2.4.0

After running:

lambda2 searchp --query pro_test.fa --index ./protein.lambda/ --output-columns 'std lcataxid'

I receive:

Reading index properties... done.
Detecting query alphabet... aminoacid detected.
Checking memory requirements... met.
Loading Subj Sequences... done.
Loading Subj Ids... done.
Loading Database Index... done.
Loading Subject Taxonomy IDs... done.
Loading Subject Taxonomic Tree... done.
done.
Loading Query Sequences and Ids... done.
Searching and extending hits on-line...progress:
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
|...~/lambda/src/search_misc.hpp:272 FAILED! (One of the paths didn't lead to root.)

stack trace:
0 [0x4c4a89] lambda2()
1 [0x47b306] lambda2()
2 [0x6662a8] lambda2()
3 [0x55680b] lambda2()
4 [0x7f5dbd0c9cbf] GOMP_parallel + 0x3f
5 [0x5ebbd8] lambda2()
6 [0x4c9436] argConv0(LambdaOptions&) + 0xfa6
7 [0x4e470a] searchMain(int, char const**) + 0x31a
8 [0x44d632] main + 0x1e2
9 [0x7f5dbdfbd830] __libc_start_main + 0xf0
10 [0x44e229] _start + 0x29

Aborted (core dumped)