Q-grid not compatible

[luonn]

Dear developers:
When using the Yambopy to generate the ndb.elph_gkkp* files of Si, I found a problem. using 6*6*6 k-points and 3*3*3 q-points (qe6.1, yambo4.2.1) to generate a uniform q-grid, the q-grid not compatible, shown as follows:
___ __ _____ __ __ _____ _____
| Y || _ || Y || _ \ | _ |
| | ||. | ||. ||. | / |. | |
\_ _/ |. _ ||.\_/ ||. _ \ |. | |
|: | |: | ||: | ||: | \|: | |
|::| |:.|:.||:.|:.||::. /|::. |
`--" `-- --"`-- --"`-----" `-----"


<---> [01] CPU structure, Files & I/O Directories
<---> [02] Y(ambo) P(ost)/(re) P(rocessor)
<---> [03] Core DB
<---> :: Electrons : 8.000000
<---> :: Temperature [ev]:0.9500E-3
<---> :: Lattice factors [a.u.]: 5.150000 5.150000 5.150000
<---> :: K points : 16
<---> :: Bands : 40
<---> :: Symmetries : 48
<---> :: RL vectors : 9377
<---> [04] K-point grid
<---> :: Q-points (IBZ): 1
<---> :: X K-points (IBZ): 16
<---> [05] CORE Variables Setup
<---> [05.01] Unit cells
<---> [05.02] Symmetries
<---> [05.03] RL shells
<---> [05.04] K-grid lattice
<---> [05.05] Energies [ev] & Occupations
<---> [06] == Electron-Phonon Interface: PW->Yambo Databases ==
<---> PW(ELPH) databases ...[PHONON] ...found 4 NOT Q-grid compatible
<---> ELPH databases (WRITE) |########################################| [100%] --(E) --(X)
<---> :: Modes : 6
<---> :: Bands range : 40
<---> [07] Game Over
and when using a random q-point sampling, the problem still exist. But, when using 2*2*2 k-points and 2*2*2 q-points (qe6.1, yambo4.2.1), the Q-grid is compatible.
Is there anything wrong?

Bests!

Nannan Luo