Fail to manage properly the Free Memory on Sipy

[pevrard]

Good Day All,
I've developed several python scripts around pytrack, one of it expecting to log the tracked GPS position. I'm using several _thread for this, however, i'm having some memory problems...
In some circumstances it works, reload the Sipy.. and then suddenly a memory error occurs.. (even sometimes without modifying any scripts) - see below.
I do understand the free memory information is not the only parameter to take into account, rather the max blk & free sz... however, i do not find a way to manage it properly...
There must be something i'm doing wrong.. but... did not find it..
Thanks for your kind help
Regards
Patrick

Traceback (most recent call last):
File "main.py", line 7, in <module>
MemoryError: memory allocation failed, allocating 565 bytes
Pycom MicroPython 1.18.3 [v1.8.6-849-d19c9e9] on 2019-09-15; SiPy with ESP32
Type "help()" for more information.

import('micropython').mem_info()
stack: 768 out of 7168
GC: total: 67008, used: 50656, free: 16352
No. of 1-blocks: 524, 2-blocks: 73, max blk sz: 384, max free sz: 154