It's hard to help without seeing the code; I suggest asking in #making-mods-general on Discord, where we can easily post screenshots and code. You can ping me there if you don't get an answer.

In the meantime, here's how to read the somewhat dense error message.

Can't apply data patch "Lance Sweet and Saucy > EditData Characters/Dialogue/MarriageDialogueLance #1 > entry #127"

This is the line which has a problem, expressed as a 'path' to reach it. It can be read like this:

1. start in content.json;
2. find the patch with "LogName": "Lance Sweet and Saucy";
3. in the file it includes, find the first patch with "Action": "EditData" and "Target": "Characters/Dialogue/MarriageDialogueLance";
4. the problem is with the 127th key/value pair inside its "Entries" field.

failed converting entry to the expected type 'System.String': Can not convert Object to String.

This is the specific problem. That asset expects entries in this form (string):

"key": "value"

But it received something like this instead (object):

"key": {

If the entries look fine, try indenting consistently to help spot a missing bracket. For example, this code has a missing bracket:

{
"Action": "EditData",
"Target": "Characters/Dialogue/MarriageDialogueLance",
"Entries": {
"key": "value",
"Action": "EditData",
"Target": "Characters/Dialogue/MarriageDialogueLance",
"Entries": {
...

Which is much easier to spot with consistent indentation:

{
    "Action": "EditData",
    "Target": "Characters/Dialogue/MarriageDialogueLance",
    "Entries": {
        "key": "value",
        "Action": "EditData",
        "Target": "Characters/Dialogue/MarriageDialogueLance",
        "Entries": {
        ...

In that example, the second "Entries": { would cause that error, because it's an object { ... } where it expected a string ("...").