Saying that the Novus Ordo rites are doubtful is an understatement.  If the only change was the dropping of the “ut” we could say the rite was doubtful because it failed to meet the minimum requirements for validity set forth by Pope Pius XII in the 1940s.  But the changes were much more extensive and substantial than that.  Pope Leo found that the Anglican rites were “absolutely null and utterly void” (doubtlessly invalid).  Arguably the Novus Ordo is more egregiously deformed than the Anglican rites.  Read Fr Cekada’s response to Fr Pierre-Marie.  In fact when I read Fr Pierre-Marie’s article before reading Fr Cekada’s I was already convinced that it was invalid.  The first half of Fr Pierre-Marie’s article paints a horrifying picture of the Novus Ordo rite that nothing written in the second half was able to convince me it was valid.

Or if there is anyone else, such as Judith 15 Ten, who can explain in their own words why they believe new rite is invalid, I would be interested in hearing it.  

The reason I'm asking is because everyone I know of who doubts the validity of the new rite does so because others doubt it, and not for doctrinal reasons.   And those I know who don't merely doubt, but positively affirm that the new rite is invalid, likewise don't do so for solid doctrinal reasons, but because the doubts of others have so persuaded them that they eventually because certain it is invalid.

But we're not talking about an act of faith (believing a truth), but refusal to believe something due to doubts of others.  

X: Very few are illumined by infused knowledge.  And in such difficult matters, only a very rash person would concoct his own theology.

Reply: I am not suggesting that anyone concoct his own theology.  Why would anyone do that when we have the Church's sacramental theology to guide us? The reason for studying the Church's theology is precisely because we don't have infuse knowledge.

X: The whole raisin d’etre of authority is to serve and protect truth, so why should a Catholic be shamed for embracing the guidance of well formed authorities?  As for myself, I make Bishop Tissier’s doubts my own.  Whether I quote his words, or reformulate them in my own makes no difference:  He doubts, and I find his reasons for doubting persuasive.

Reply: But doubting because he doubts is not an act of submission to authority.   Has he commanded you to doubt?  I "doubt" it.  If he did command you to doubt was it a legitimate act of authority, and does he even have any legitimate claims of authority over you?
Your position is not that of submission to authority, but of doubting because someone else doubts.  That's the same reason almost everyone else I have spoken about this with has given for doubting, or positively denying, the validity of the new rite of episcopal consecration.  
 

Or if there is anyone else, such as Judith 15 Ten, who can explain in their own words why they believe new rite is invalid, I would be interested in hearing it.  

The reason I'm asking is because everyone I know of who doubts the validity of the new rite does so because others doubt it, and not for doctrinal reasons.   And those I know who don't merely doubt, but positively affirm that the new rite is invalid, likewise don't do so for solid doctrinal reasons, but because the doubts of others have so persuaded them that they eventually because certain it is invalid.

It looks like you are reading the objections as if they are Fr. Pierre-Marie's own arguments.  Those objections do not reflect his position.  They are the objections of others that he refutes later in the article.  

His article is structured like the Summa. He proposes objections, then answers the question, and then lastly replies to the objections.

Fr. Pierre-Marie does not believe the new form is invalid, or even doubtful.  On the contrary, he said: "It can be concluded that the formula is certainly valid, for it has been utilized from time immemorial in numerous Eastern Rites; it means the gift of the Holy Ghost that creates the bishop."

Here's a link his replies to the objections you mentioned.  http://sspx.org/en/validity-new-rite-episcopal-consecrations-5

He begins by stating the facts.  He never refutes the facts.  He admits them.  The form does not meet the minimum requirements set forth by Pius XII.  The form is based on an episcopal installation ceremony that Dom Botte erroneously thought was a consecration ceremony.  The rite is not the same as the eastern rites.  He refutes none of that because those are facts that he admits are true.

Ah, okay I see what you mean by submitting to his authority.  

Do I think you should doubt simply because he has doubts?  No, not without doing your own homework.  

There are a lot of trustworthy and intelligent people who have not had any doubts about the validity of the new rite, such as Cardinal Ottaviani, so it strikes me as imprudent to doubt simply because someone you consider trustworthy and intelligent doubts.  

What I think you should do is find out what issues cause him to doubt, and then thoroughly investigate those matters yourself.  Then, after doing so, you might doubt for the same reasons he doubts, but not simply because he doubts.