twsearch cannot find optimal solution for some specific positions.

[coldsun0630]

File 1. "FTO-test_puzzle.tws"

Name FTO-test_puzzle

Set CORN 6 2
Set EDGE 12 1
Set TRIA 12 1
Set TRIB 12 1

Solved
CORN
1 2 3 4 5 6
0 0 0 0 0 0
EDGE
1 2 3 4 5 6 7 8 9 10 11 12
TRIA
1 2 3 4 5 6 7 8 9 10 11 12
TRIB
1 2 3 4 5 6 7 8 9 10 11 12
End

Move R
CORN
1 3 5 4 2 6
0 0 1 0 1 0
EDGE
1 2 3 6 4 5 7 8 9 10 11 12
TRIA
1 7 8 4 5 6 12 10 9 3 11 2
TRIB
1 2 3 6 4 5 7 8 9 10 11 12
End

File 2. "FTO-test_pos.scr"

Scramble FTO-test_pos
CORN
1 3 5 4 2 6
0 0 1 0 1 0
EDGE
1 2 3 6 4 5 7 8 9 10 11 12
TRIA
1 7 8 4 5 6 12 10 9 3 11 2
TRIB
1 2 3 6 4 5 7 8 9 10 11 12
End

File 3. "FTO-test_scr.scr"

ScrambleAlg FTO-test_scr
   R
End

==========

Log 1. Solving a scramble algorithm "R"

DESKTOP% ./build/bin/twsearch -M 49152 -t 14 --mindepth 1 --maxdepth 3 --alloptimal "samples/main/FTO-test_puzzle.tws" "samples/main/FTO-test_scr.scr"
# This is twsearch v0.6.6-264-gff84160 (C) 2022 Tomas Rokicki.
# ./build/bin/twsearch -M 49152 -t 14 --mindepth 1 --maxdepth 3 --alloptimal samples/main/FTO-test_puzzle.tws samples/main/FTO-test_scr.scr
Created new moves R'
State size is about 1.58261 x 10^29 log2 96.9982
Requiring 152 bits 20 bytes per entry; 20 from identity.
Found 2 canonical move states.
Calculated canonical states in 0.00203609
For memsize 51539607552 bytesize 51539607552 subshift 2 memshift 26 shardshift 32
Trying to allocate 51539607616
Initializing memory in 0.00166297
Filling depth 0 val 0 saw 1 (1) in 0.000237942 rate 0.00420271
Filling depth 1 val 0 saw 2 (2) in 0.000139952 rate 0.0142906
Filling depth 2 val 0 saw 0 (0) in 0.000115156 rate 0
Filling depth 3 val 0 saw 0 (0) in 0.000110865 rate 0
Solving FTO-test_scr
 R'
Found 1 solution max depth 1 probes 4 nodes 3 in 2.81334e-05 rate 0.14218
Twsearch finished.

Log 2. Solving a position equivalent to "R"

DESKTOP% ./build/bin/twsearch -M 49152 -t 14 --mindepth 1 --maxdepth 3 --alloptimal "samples/main/FTO-test_puzzle.tws" "samples/main/FTO-test_pos.scr"
# This is twsearch v0.6.6-264-gff84160 (C) 2022 Tomas Rokicki.
# ./build/bin/twsearch -M 49152 -t 14 --mindepth 1 --maxdepth 3 --alloptimal samples/main/FTO-test_puzzle.tws samples/main/FTO-test_pos.scr
Created new moves R'
State size is about 1.58261 x 10^29 log2 96.9982
Requiring 152 bits 20 bytes per entry; 20 from identity.
Found 2 canonical move states.
Calculated canonical states in 0.000946999
For memsize 51539607552 bytesize 51539607552 subshift 2 memshift 26 shardshift 32
Trying to allocate 51539607616
Initializing memory in 0.000812054
Filling depth 0 val 0 saw 1 (1) in 0.000231028 rate 0.00432849
Filling depth 1 val 0 saw 2 (2) in 0.000151873 rate 0.0131689
Filling depth 2 val 0 saw 0 (0) in 0.000128984 rate 0
Filling depth 3 val 0 saw 0 (0) in 0.000118017 rate 0
Solving FTO-test_pos
No solution found in 0
Twsearch finished.

==========

This doesn't happen and outputs as expected, when the move (which both in .tws and .scr file) contains no orientations, like:

Move F
CORN
1 2 4 5 3 6
0 0 0 0 0 0
EDGE
1 10 3 4 5 2 7 8 9 6 11 12
TRIA
1 2 3 4 5 6 9 7 8 10 11 12
TRIB
1 10 11 3 5 2 7 8 9 6 4 12
End

==========

Just in case, here are the exact files I've used. (The 3 files above are zipped into "FTO-test.zip"):
https://mega.nz/file/hUsFTAxB#YZn29-wJJfVdOInztp7zTxjIGA06A4lWqtFUkTETE6U

[coldsun0630]

I found this also happens for non-1-move positions. For example:

For this .scr, twsearch succeeds to find 2 solutions in total ("U d'", "d' U"):

Scramble FTO-Uv_pos
CORN
3 1 2 5 6 4
0 0 0 1 0 1
EDGE
4 5 6 7 8 9 1 2 3 11 12 10
TRIA
3 1 2 7 8 9 10 11 12 4 5 6
TRIB
4 5 6 7 8 9 1 2 3 11 12 10
End

But for this .scr, twsearch fails to find any ≤3 moves solution:

Scramble FTO-Rv_pos
CORN
4 3 5 6 2 1
1 0 1 0 1 1
EDGE
10 11 12 6 4 5 2 3 1 9 7 8
TRIA
9 7 8 5 6 4 12 10 11 3 1 2
TRIB
10 11 12 6 4 5 2 3 1 9 7 8
End

[coldsun0630]

I have to note that the Move d (in that custom def) also contains orientation vectors:

Move d
CORN
1 2 3 6 4 5
0 0 0 1 0 1
EDGE
1 8 9 4 2 3 7 5 6 12 10 11
TRIA
1 2 3 10 11 12 4 5 6 7 8 9
TRIB
1 2 9 4 5 3 7 8 6 12 10 11
End