The reason the writing changed so much is gone into in detail in this book: https://www.amazon.com/Shooting-Columbo-Deaths-Rumpled-Detective/dp/1937878112 Basically Peter Falk was getting bored. And the new writer who came on board that he took a liking too wanted to expand the character. And thus the changes. It's a really interesting read.
I spent like 20 minutes searching for that episode and still couldn't find it.
The book below might be of interest tho. The first half of the book discusses how the character came to be, Inspirations for the character, and how the culture at the time contributed to the success of columbo. Theres a free copy on z library that i can send to you through dm's if you want.
https://www.amazon.com/Columbo-Rhetoric-Inquiry-Resistant-Responders/dp/1783209852
This is from Jenny Hammerton's book, which compiles recipes either devised by or generally about the various actors on Columbo. https://www.amazon.com/Cooking-Columbo-Suppers-Shambling-co-stars/dp/1981417427 The eBook's great, a lot of research went into it, certainly worth $4 USD.
I bought the Japanese blu ray set and it included everything, in HD. But you might need a region free player to watch it. Idk, I ripped the discs with makemkv.
Columbo is such a rare case of a really really good show that the AI consumer watchdog bots think they are fake reviews lol. I'm not saying there might not be fake reviews but I kinda doubt they are prevalent enough to bring it to a 3.5
If you guys don't trust OP and want a non-affiliate/ref link you can use this one: https://www.amazon.com/Columbo-Complete-Peter-Falk/dp/B07B64Z7HQ
What a stud. I just finished reading his autobiography / memior. It is excellent, a must read if you're a fan! Amazon link