How to create a list to input to mc.line~ and how to identify the cause of the patch crash.

Hi,everyone

Currently, I'm creating a patch where I select a range from an audio file (in waveform A), further narrow and confirm that range (in waveform B, the selected area turns green), and then press bang (start playing) to perform granular programming for the time specified in the float numberbox (duration of phrase (ms)). At that time, by inputting the list created by the structure above in mc.line~ @chans 8 from mc.target to mc.line~ @chans 8, the granular programming should not be simple, but rather each channel should change speed at different points. I'm currently creating such a patch, but when I test it by turning on mc.dac~ and performing the above steps and then pressing bang (start playing), the patch crashes instantly every time. First, I'd like to know the cause of this. Also, I always struggle with inserting commas "," when creating line~-related lists. Is there an object that can handle lists of packs using only standard objects (because I need to use it with my school's max msp)? If not, is there a smarter way than the current method of stacking two prepend objects?

I would appreciate any advice you can offer.